Abstract: The coagulation method is of great importance in preparation of concentrated emulsion. The present study is devoted to the following items:1. Synthesis of different modified gelatins2. Evaluation of physical property3. Coagulating performance4. Recovery per cent of PA gelatin and silver halide5. Sensitometric characteristic of emulsion prepared with PA gelatin Modified gelatin is superior to other kinds of copolymer coagulating agent such as polystyrene sulfonate resin due to low cost, shorter induction period to start coagulation, narrower coagulating pH range, less loss of silver halide and better sensitometric property of the emulsion.