Chitinase has been purified from the extract of cabbage stems with roots through successive steps of ammonium sulfate fractionation, Sephadex G‐75 gel filtration, chromatofocusing and Sephacryl S‐200 HR gel filtration. By these steps, the purity of the enzyme increased by 63 fold and the recovery of the enzyme activity was 18%. The purified enzyme was homogeneous when analyzed by SDS‐PAGE#. It showed an optimal pH of 6 and optimal temperature of 60°C for hydrolysis of ethylene glycol chitin (EGC). The molecular mass of the enzyme was 41 kDa, as determined by SDS‐PAGE. Heavy metal ions (1.5 mM) Ag+, Hg2+ and Fe2+, and chemical modification agents NAI (1 mM), NBS (0.5 mM) and CHD (0.5 mM) significantly or completely inhibited the activity of the enzyme. Substrate EGC at high concentrations also inhibited the activity. BSA (0.05%), Triton X‐100 (0.5%) and glycerol (50%) provided significant protection of the enzyme from freezing inactivation.