The characteristics of the pumping light distribution in working medium side-pumped by diode bars with different pumping structure is analyzed in this paper. With computer modeling and experimental test, the gain distribution characteristics in the working medium side-pumped by two different pumping structures is discussed by means of studying the proportion relationship between the absorbed pumping energy and the area needed. The comparison result illustrates that the homogeneity of the pumping light distribution in working medium is better in quasi-trapezoid diode structure.