The activity sounds of rice weevil Sitophilus oryzae (L.) adults, maize weevil Sitophilus zeamais (Motschnlsky) adults and rice weevil larvae in wheat,corn and coix seeds were respectively sampled. The power spectrum characteristics were analyzed and their differences in different temperatures were studied. The result shows that at 27 ℃, the frequencies of activity sound power spectrum peaks of rice weevil adults in wheat are 172.3 Hz， 409.1 Hz and 1 077.0 Hz. The frequencies of activity sound power spectrum peaks of maize weevil adults in wheat are 193.8 Hz， 430.7 Hz and 990.5 Hz. The frequencies of activity sound power spectrum peaks of maize weevil adults in corn are 236.9 Hz and 1 012.0 Hz. The frequencies of activity sound power spectrum peaks of rice weevil larvae in coix seed are 344.5 Hz and 990.5 Hz. On the other hand, the study result also shows that both the insect species and grain species affect the activity sound characteristics of grain insects, and the frequency ranges of activity sound power spectrum peaks in different temperatures are different. The experiment results provide data for the establishment of sound characteristic database of stored grain insects and the establishment of insect automatic detection.