A new measuring method of transverse mode configuration in a laser beam is presented. It is based on the spatial relative intensity distribution of laser field. The simulation indicates that the measuring method is feasible. An experiment is also conducted to measure transverse mode configuration for a Q-switched laser diode pumped solid state laser (DPL). Without cavity parameters, the transverse mode proportion is figured out with these testing data by using this new measuring method. Based on this measured transverse mode proportion, the laser beam is also reconstructed theoretically, and it agrees well with the spatial transmission of the laser beam for measuring.