In laser diode end-pumping solid-state lasers, the departure gene is introduced to describe the coaxial degree betweem the pumping light and the columniform laser crystal. The effects of the departure gene on the gain efficient of the oscillating modes and output beam quality are analyzed in theory, and the corresponding experiment is done with the fiber coupling diode lasers end-pumping Nd:YAG lasers. The results of the theory are in accordance with that of experiment: the departure gene is smaller, the gain of lower order mode becomes higher and the output beam quality changes better. Therefore, in order to obtain the lower order mode output with higher gain and better beam quality, control the coaxial degree between the pumping light and laser crystal is an important measure besides holding proper resonat cavity.