In this paper, by the computer simulation of the structure of amorphous alloy, the influence of the size ratio of M atoms to TM atoms on the structure of amorphous alloy TM100-xMx is studied with almost the same composition. For this purpose, the structures of amorphous alloy Fe80P20, Co81P19 and Fe80B20 are simulated, and the influence of the change of the atomic size ratio on the structures of amorphous alloy is analyzed based on the partial reduced distribution function, topologic short-range order, stabilization of structurc and the change of atomic size by the electron transfer etc.