Abstract: Objective To make gray sequence analysis of the ecological factors to the population fluctuation of Tyrophagus putrescentiae. Methods Samples of T.putrescentiae and its natural enemy were collected， examined and counted in every ten days， relative humidity and temperature were recorded simultaneously. Data were analyzed by gray sequence analysis. Results The population of T.putrescentiae in the wheat warehouse reached peaks in late June and mid-September respectively， and that of the predatory mites showed a following efficiency. The gray sequence of the eco-logical factors to the larvae of T.putrescentiae was temperature＞natural enemy＞relative humidity; to the nymphs and adults, it was relative humidity＞natural enemy＞temperature; and to the population, it was relative humidity＞temperature＞natural enemy. Conclusion Relative humidity， temperature and natural enemy were important ecological factors affecting the population dynamic of T.putrescentiae, and the prevalence curve of T.putrescentiae shows a bimodal pattern.

Key words: Tyrophagus putrescentiae, Gray sequence, Population dynamics