The activity sounds of Sitophilus zeamais adults in wheat, corn and Sitophilus oryzae larvae in coix seed were respectively sampled in different temperatures, and decomposed by wavelet packet. Three characteristics of decomposition nodes were analyzed. They were nodes energy, nodes energy ratio and energy entropy. The research found that the nodes energy and nodes energy ratio of the activity sound of Sitophilus zeamais adults in wheat and corn were greatly different in the same temperature, and the difference of frequency distribution between these two types of signals was obtained. It was also found that there was much difference between the energy entropy of these two types of signals, and the activity acoustic signal energy entropy mean statistical data of Sitophilus zeamais in wheat and corn were collected. In different temperatures, the nodes energy, nodes energy ratio and energy entropy of the activity sound of Sitophilus oryzae larvae in coix seed were also different. The results show that both the difference of temperature and grain species affect the activity sound characteristics of grain insects, and the activity sounds in wavelet packet decomposed characteristics are significant different.