Tetrachloroethene (PCE), trichloroethene (TCE) and carbon tetrachloride (CT) were selected as target contaminants in this paper. Experiments were conducted to determine the effectiveness of zero-valent iron on dechlorination reaction and reaction-affecting factors in different mixing conditions. The results show that selected iron scrapes were effective in the dechlorination of chlorinated aliphatics, especially for chlorinated alkanes, and dechlorination reaction was pseudo first order. When PCE and TCE coexist, the reaction rate constant (K) was 0.0624 mL.(m2.h)-1 and 0.0357 mL.(m2.h)-1 respectively, showing the higher the chlorinated degree the quicker the reaction. When CT and PCE coexist, K was 0.1341 mL.(m2.h)-1 and 0.0129 mL.(m2.h)-1 respectively; compared with PCE, CT was degraded much more quickly and thoroughly giving an account of alkane was prior to alkene in dechlorination when at the same chlorinated degree. Either chlorinated alkanes or alkenes, their degradation half-lives were lower in monocomponent condition than coexisting with other component.