A light source driving circuit of light emitting semiconductor and a backlight module are provided. The light source driving circuit of light emitting semiconductor includes a driving control circuit and a constant current driving circuit coupled to the driving control circuit for controlling a current flowing through the light emitting semiconductor. When the driving control circuit receives a display-mode-switch signal which has an indication for switching from a present display mode to a new display mode, the driving control circuit controls the constant current driving circuit such that in the process of switching from the present display mode to the new display mode, the current flowing through the light emitting semiconductor changes gradually.