Abstract: Suzhou Rail Transit Line 1-Line 4 main substation set-up situation is introduced. The influence of failure exit of a single main substation on power supply of each line and the correspondent power supply adjustment strategy is simulated and analyzed. The principle of line network power supply mode adjustment under condition of main substation failure is proposed. Key items in power supply mode adjustment that require attention is summarized. The advantages and disadvantages of various adjustment strategy are compared and analyzed, and the choice conditions are given.