In order to determine the contents of chlorine in the fume of warships on fire, the method of AgCl turbidity is improved by adding appropriate dispersing agent and surface active agent such as sodium dodecyl benzene sulphonate (DBS), poly(vinyl alcohol) (PVA) and twein-80. The results show that the stability and sensitivity of the system are improved, and the detection limit is decreased from 3.5×10^-1mg/L to 3.1×10^-2mg/L. The improved method has wide linear range and high reproducibility.