Abstract: Aiming at the problem that it is difficult to improve the grade of phosphate concentrate in a high magnesium and high silica gel collophonite in Yunnan，an experimental study on the beneficiation pro⁃ cess was carried out. The optimum grinding fineness and mixed acid dosage were determined by single factor condition test，and the reverse flotation combined collector was optimized by simplex lattice mixing design method. The ratio of cetyl trimethyl ammonium bromide，octadecyl dimethyl tertiary ammonium and dodecylamine was used as independent variables，and the grade and recovery rate of phosphate concentrate were used as response dependent variables for fitting. The test results show that the specific gravity of do⁃ decylamine has the greatest influence on the grade and recovery of phosphate concentrate. The optimal ratio of combined collector cetyltrimethylammonium bromide : octadecyl dimethyl tertiary ammonium : dodecylamine optimized by response surface method is 18∶13∶69. On this basis，combined with the best single fac⁃ tor conditions，a phosphate concentrate with P₂O₅ grade of 31.14% and recovery rate of 80.21% can be obtained by one roughing，one scavenging and one cleaning reverse flotation closed-circuit test，which solves the problem that the quality of the collophane product is not up to the standard.

Key words: collophonite, reverse flotation, response surface method