Using EDTA titrimetric method to determine the calcium content in ferrosilicon nitride has been researched in this paper. The sample was digested with nitric acid and hydrofluoric acid in high-pressure pot. And the silicon and fluorine in the sample solution was removed by smoking with the perchloric acid. The iron and aluminum in the sample solution was precipitated and separated by adding ammonia and hexamethylenetetramine. At last the calcium was titrated with EDTA standard solution. Some condition experiments were also carried out,which included decomposition of the sample,the interference of coexisting elements and the eliminating method,and the optimal conditions were obtained. The precision and accuracy of the method were tested by using some ferrosilicon nitride standard samples. The average value of the results was in the allowable range of SD of the standard samples,and the RSD was less than 5%.