Abstract: By using silicate bacteria, orthoclase and biotite, we studied the effects of adsorption time and silicate bacteria concentration on adsorption amount on mineral surface of orthoclase, biotite and their coexistence. The results show that the maxima of adsorption amount per unit area of silicate bacteria on orthoclase and biotite are 40 min and 30 min for bacteria concentration 25×106 /ml and 30×106 /ml, respectively. Both in the system of single mineral system and in the coexisting system, the adsorption amount per unit area of silicate bacteria on orthoclase is always higher than that on biotite. In the coexisting system, silicate bacteria prefer to be adsorbed on the surface of orthoclase. While concentration of silicate bacteria increases, the selective adsorption on orthoclase becomes more dominant. The results provide important evidence for the bioweathering mechanism of minerals.