In the production of chemical synthesis granular tripe superphosphate（TSP）,ammonia is added into the cooler toneutralize a small amount of free acid for improvement of the quality of the product,which leads to the problems of high tem-perature of particles at the outlet and easy caking etc..The research idea of neutralizing free acid with ammonia and adding caustic calcined magnesia（referred to as bitter soil） in granulator was put forward,and the industrial test was carried out.Re-sults showed that the mass fraction of free acid in the finished product was less than 3% by adding liquid ammonia 5.0 kg/t（calculated by 1 t TSP）+bitter soil 10.0 kg/t（calculated by 1 t TSP）,which met the standard requirement of export TSP.Atthe same time,reducing the raw material temperature,the product caking was effectively improved.