The optical absorption properties of the two-dimensional (2D) MoSi₂N₄ monolayer is often a focus of research. By semi doping Cr and W at M sites, the influence of M-site atoms on the optical absorption properties of MA₂Z₄ series materials was investigated. The results show that the atomic layer spacing of 2D materials has some changes after the semi doping of the Cr and W elements, but the entire crystal structure is not significantly different. The semi doping of Cr atoms makes the MoSi₂N₄ monolayer have an additional absorption peak, the highest absorption peak of the Mo_0.5Cr_0.5Si₂N₄ monolayer has a large red shift corresponding to the wavelength, and the width of the absorption peak is also greatly improved. The semi doping of W element results in a red shift of the strongest absorption peak and an increase of the maximum absorption intensity of the Mo_0.5W_0.5Si₂N₄ monolayer.