This paper presents an inseparability criterion for continuous variable systems based on the total variance of a pair of Einstein-Podolsky-Rosen (EPR) type operators. The criterion provides a sufficient condition for entanglement of any two-party continuous variable states. Furthermore, for all Gaussian states, this criterion turns out to be a necessary and sufficient condition for inseparability. Quantum entanglement plays a crucial role in quantum information theory. Checking whether a state is entangled is important, and Peres proposed a criterion based on the partial transpose of the composite density operator, which provides a sufficient condition for entanglement. However, this criterion is not necessary for higher dimensional states. The authors propose a simple inseparability criterion for continuous variable states based on the total variance of EPR-type operators. They find that for any separable continuous variable states, the total variance is bounded from below by a certain value resulting from the uncertainty relation, whereas for entangled states this bound can be exceeded. Violation of this bound provides a sufficient condition for inseparability. For Gaussian states, the authors show that compliance with the lower bound by a certain pair of EPR-type operators guarantees that the state has a P-representation with positive distribution, so the state must be separable. Hence, they obtain a necessary and sufficient inseparability criterion for all Gaussian continuous variable states. The authors prove that for any separable quantum state, the total variance of a pair of EPR-like operators satisfies a certain inequality. They also show that for Gaussian states, this inequality provides a necessary and sufficient condition for inseparability. The paper concludes with an example showing how the criterion can be applied to a two-mode squeezed vacuum state. The result shows that if there is only vacuum fluctuation noise, the initial squeezed state is always entangled. However, if thermal noise is present, the state may become separable.This paper presents an inseparability criterion for continuous variable systems based on the total variance of a pair of Einstein-Podolsky-Rosen (EPR) type operators. The criterion provides a sufficient condition for entanglement of any two-party continuous variable states. Furthermore, for all Gaussian states, this criterion turns out to be a necessary and sufficient condition for inseparability. Quantum entanglement plays a crucial role in quantum information theory. Checking whether a state is entangled is important, and Peres proposed a criterion based on the partial transpose of the composite density operator, which provides a sufficient condition for entanglement. However, this criterion is not necessary for higher dimensional states. The authors propose a simple inseparability criterion for continuous variable states based on the total variance of EPR-type operators. They find that for any separable continuous variable states, the total variance is bounded from below by a certain value resulting from the uncertainty relation, whereas for entangled states this bound can be exceeded. Violation of this bound provides a sufficient condition for inseparability. For Gaussian states, the authors show that compliance with the lower bound by a certain pair of EPR-type operators guarantees that the state has a P-representation with positive distribution, so the state must be separable. Hence, they obtain a necessary and sufficient inseparability criterion for all Gaussian continuous variable states. The authors prove that for any separable quantum state, the total variance of a pair of EPR-like operators satisfies a certain inequality. They also show that for Gaussian states, this inequality provides a necessary and sufficient condition for inseparability. The paper concludes with an example showing how the criterion can be applied to a two-mode squeezed vacuum state. The result shows that if there is only vacuum fluctuation noise, the initial squeezed state is always entangled. However, if thermal noise is present, the state may become separable.