Two pretreatment methods，boilingwater extraction suggested in GB/T 24890—2010 and ultrasonic extraction，are comparatively used to extract the chloride ions in the samples.The best test conditions of determining the chloridion level in compound fertilizers by mercury nitrate titration are determined，and the results are almost in accord with that of silver nitrate titration.However，the operation of mercury nitrate titration is relatively simple，and the titration end point is stable，easy to judge，the recovery rates of mercury nitrate titration are in the rage of 94.5%~103.3% and the accuracy is also higher.Besides，combining with mercury nitrate titration，the escadasemimelting method is firstly used to determine the total chlorine level in compound fertilizers，which is consistent with the method of determination of chlorine by means of a silver nitrate titration method used mixed flux（Na2CO3 and MgO blended with 1∶2）in GB 18877—2009 “organicinorganic compound fertilizer”.They are suitable for determining the total chlorine level in compound fertilizers and organicinorganic compound fertilizer whose extracting solution are turbid or colorful and the endpoint is uneasy to judge by boilingwater extraction and ultrasonic extraction.Most of all，the method has the many merits，such as batch melting samples，less interference and high accuracy.