Abstract: The study with routine microbiological methods showed that there existed certain amounts of thermophilic bacteria and thermophilic protease-producing bacteria in normal temperature environments. Compared with water body, soil was relatively rich in thermophilic bacterial resources, and thermophilic protease-producing bacteria were richer in fertile than in unfertile soil. In water environment, whether in lake, river and treated waste water, there were definite amounts of thermophilic bacteria and thermophilic proteases-producing bacteria under normal temperature, and the proportion of thermophilic protease-producing bacteria to thermophilic bacteria in the aeration phase of beer wastewater reached 45%. A highly active thermophilic protease-producing strain was screened, with its protease activity reached 642 U·ml^-1 at pH 7.6 and 68 ℃. This study was of significance for the exploitation of thermophilic protease-producing bacterial resources, and their application in industry and in environmental protection.

Key words: Qiandao Lake, Chlorophyll a, Multiple stepwise regression, Trophic state index