Coagulant polyaluminum chloride (PAC) and coagulant polyaluminum chloride-chitosan (PAC-CTS) were prepared under different conditions. The influence of Al distribution in different coagulants of B value, preparing temperature and C value were studied. The aluminum species were measured via the application of Al-Ferron timed spectrophotometric method. It showed that the reaction rate of PAC and Ferron assay and Alb content increased with B value, which decreased with temperature and C value. Combined with experimental progress and economy, the optimum conditions of preparing PAC-CTS are T=50℃, B=2.0, C=1/20.