A field experiment was conducted in 2004 to investigate effects of the system of rice intensification (SRI) on soil biological properties. The treatment was compared with the control (TF, Traditional Flooding) in soil cultureable microorganisms (bacteria, fungi, actinomycetes), microbial biomass C and N, soil enzyme (urease, invertase, alkaline phosphatase, catalase) activity and soil available N and P. Treatment SRI was significantly higher than the control in population of cultureable microorganisms, microbial biomass C and N, regardless of sampling date and 12.6%, 30.0%, 15.1% and 13.8% higher in activity of urease, alkaline phosphatase, invertase and catalase, respectively at the tillering stage. The treatment was also higher than the control in soil available N, and however, showed no significant difference in soil available.