The paper presents the background field method for multi-loop calculations in gauge field theories, extending its application beyond one-loop processes. The method retains explicit gauge invariance by fixing a gauge for the quantum field while keeping the background field gauge invariant. The authors derive the relationship between the gauge-invariant effective action computed using this method and the conventional effective action. They provide Feynman rules and discuss renormalization, showing that renormalization can be performed without reference to fields inside loops. The renormalization of the gauge coupling constant, background field, and gauge-fixing parameter is addressed, with the gauge-fixing parameter renormalization avoidable by using the Landau-type background field gauge. The method simplifies calculations, particularly for the two-loop contribution to the β function in pure Yang-Mills theory, where only the background field two-point function is needed. The paper concludes with a detailed example of the β function calculation, demonstrating the method's effectiveness and simplifications over conventional approaches.The paper presents the background field method for multi-loop calculations in gauge field theories, extending its application beyond one-loop processes. The method retains explicit gauge invariance by fixing a gauge for the quantum field while keeping the background field gauge invariant. The authors derive the relationship between the gauge-invariant effective action computed using this method and the conventional effective action. They provide Feynman rules and discuss renormalization, showing that renormalization can be performed without reference to fields inside loops. The renormalization of the gauge coupling constant, background field, and gauge-fixing parameter is addressed, with the gauge-fixing parameter renormalization avoidable by using the Landau-type background field gauge. The method simplifies calculations, particularly for the two-loop contribution to the β function in pure Yang-Mills theory, where only the background field two-point function is needed. The paper concludes with a detailed example of the β function calculation, demonstrating the method's effectiveness and simplifications over conventional approaches.