The growth kinetic process of efficient bacteria flora (FYD) for degrading unsymmetrical dimethyl hydrazine (UDMH) was simulated by Haldane kinetic model of growth inhibition. The degradation kinetic process of UDMH was simulated by Andrews noncompetitive kinetic model of substrate inhibition. The kinetic equations were fitted out, and the ratio growth rate and ratio degradation rate were calculated by the fitted equations. Results show that when the initial concentration of UDMH is 43.6980 mg·L^-1, the flora has maximum ratio growth rate. When the initial concentration of UDMH is 50.2261 mg·L^-1, the UDMH has maximum ratio degradation rate. The theoretical value is very close to the experimental one as UDMH concentration is 50 mg·L^-1. The yield coefficient that FYD degrades UDMH is 0.229, which reflects the tolerance and utilization ability of FYD to UDMH. The linear relationship between the maximum ratio growth rate and the maximum ratio degradation rate shows a material balance exists in the process of degrading UDMH by flora FYD. The change in cell growth with UDMH concentration exists bacteria rationality.