The UV absorbance ratio(A₃₉₂/A₂₈₀) was developed to survey the purity of the P450cam mutant protein during the purification of the mutants protein. Thus the course of the purification became compact and the efficiency of the purification had been improved. β-Mercaptoethenol had been developed to maintain the deoxidization of the protein during the purification. Crystals of the F87L/Y96F/L244A/V247A mutant were grown by vapor diffusion method. X-ray diffraction data were collected to 0.22 nm resolution on a Mar Research area detector in house. The structure was determined by Difference Fourier Method. The final crystallographic R factor and R_free factor are 0.197 and 0.247 respectively. The RMS deviations of bond length and angle of the mutants are 0.001 77 nm and 1.96°respectively. Structure comparison indicates that there is no obvious conformaional change between P450cam and the F87L/Y96F/L244A/V247A mutant. After mutation, the structure of the active pocket became larger but its hydrophobility increased, which are consistent with the aim of mutantion