Small signal gain coefficients(SSGC) of 93 pieces N31 Nd3+ doped glasses for Shenguang Ⅱ high power laser system are tested. Results show that the average SSGC of Nd glasses with 2.2% mass fraction of Nd2O3 and 3.0% mass fraction of Nd2O3 are 0.0387 cm-1 and 0.0416 cm-1 respectively. Gain fluctuation range of these two kinds of Nd glasses are 0.86% and 0.76% respectively. This result demonstrates that the gain fluctuation range of N31 Nd glasses meets the requests of Shenguang Ⅱ projects and definitely provides the gain equilibrium for every beam laser in this system. This experiment is a valuable experience for controlling the gain properties of even larger Nd glass in the future.