Several bacterial species have been found to involve the biomineralization phenomenon promoted by them. The formation of calcium carbonate mineral (calcification) is most abundant phenomena as biomineralization by bacteria. Here we introduce the simple assessing method of calcification catalyzed by thermophilic bacteria. To obtain the fresh biomass of thermophilic bacterium, the thermophilic bacteria was cultured on conventional nutrient agar medium at 60˚C. Fresh biomass of bacteria is simply placed on calcite promoting hydrogel surface, and incubated at 60˚C. After incubation for 24 to 72 h, a number of single crystals can be found in the biomass. This method provides simple assessing for screening of calcification upon thermophilic bacteria.