This study explores bipolarized Weyl semimetals and the quantum crystal valley Hall effect in two-dimensional alternagnetic materials. The research combines spin group symmetry analysis, lattice modeling, and first-principles electronic structure calculations to demonstrate that type-I, type-II, and type-III bipolarized Weyl semimetals can exist in alternagnetic systems. Four ideal two-dimensional type-I bipolarized Weyl semimetals, Fe₂WTe₄ and Fe₂MoZ₄ (Z=S, Se, Te), are predicted. The quantum crystal valley Hall effect is observed in Fe₂WTe₄, Fe₂MoS₄, and Fe₂MoSe₄ under spin-orbit coupling. These materials can transition from a quantum crystal valley Hall phase to a Chern insulator phase under strain. In contrast, Fe₂MoTe₄ remains a Weyl semimetal with only one pair of Weyl points under spin-orbit coupling. The position, polarization, and number of Weyl points in Fe₂WTe₄ and Fe₂MoZ₄ can be manipulated by adjusting the direction of the Néel vector. The study identifies Fe₂WTe₄ and Fe₂MoZ₄ as promising experimental platforms for investigating the distinctive physical properties of various alternagnetic topological phases. The quantum crystal valley Hall effect in these materials is attributed to the crystal symmetry, leading to opposite Chern numbers for the two pairs of valley electrons in the Γ-X and Γ-Y directions. This effect is distinct from the quantum valley Hall effect in nonmagnetic materials. The research also highlights the potential of these materials for applications in spintronics and topological quantum computing.This study explores bipolarized Weyl semimetals and the quantum crystal valley Hall effect in two-dimensional alternagnetic materials. The research combines spin group symmetry analysis, lattice modeling, and first-principles electronic structure calculations to demonstrate that type-I, type-II, and type-III bipolarized Weyl semimetals can exist in alternagnetic systems. Four ideal two-dimensional type-I bipolarized Weyl semimetals, Fe₂WTe₄ and Fe₂MoZ₄ (Z=S, Se, Te), are predicted. The quantum crystal valley Hall effect is observed in Fe₂WTe₄, Fe₂MoS₄, and Fe₂MoSe₄ under spin-orbit coupling. These materials can transition from a quantum crystal valley Hall phase to a Chern insulator phase under strain. In contrast, Fe₂MoTe₄ remains a Weyl semimetal with only one pair of Weyl points under spin-orbit coupling. The position, polarization, and number of Weyl points in Fe₂WTe₄ and Fe₂MoZ₄ can be manipulated by adjusting the direction of the Néel vector. The study identifies Fe₂WTe₄ and Fe₂MoZ₄ as promising experimental platforms for investigating the distinctive physical properties of various alternagnetic topological phases. The quantum crystal valley Hall effect in these materials is attributed to the crystal symmetry, leading to opposite Chern numbers for the two pairs of valley electrons in the Γ-X and Γ-Y directions. This effect is distinct from the quantum valley Hall effect in nonmagnetic materials. The research also highlights the potential of these materials for applications in spintronics and topological quantum computing.