Abstract: Taking AC power supply system of a mine as research object and combining possible circulation path of AC stray current, a mine AC stray current model was built based on analysis of generation mechanism of mine AC stray current. Distribution laws of AC stray current under different unbalance coefficient of insulation resistance of high voltage or low voltage cable were researched by Matlab/Simulink simulation. The research results show that when insulation resistance of high voltage or low voltage cable is asymmetry, the generated AC stray current mainly distributes in shielding or ground wire and metal net in asymmetry section of insulation resistance. When insulation resistance of the entire cable is asymmetric, AC stray current increases continuously in return path to power grid. With the increase of unbalance coefficient of insulation resistance, effective value of AC stray current flowing through shielding or ground wire, metal net and each ground electrode all increases.