The invention is related to a flotation process using an improved collector to remove alkaline earth metal carbonate impurities from phosphate ores. The flotation feed may be conditioned with the improved carbonate collector at acidic pH, and subjected to a reverse flotation. The cell overflow may be collected as waste in which carbonate minerals dominate, and the cell underflow may be the phosphate concentrate. The collector may be a combination of chemicals, comprising: (1) any kind of fatty acids, either conventional fatty acid, saponified fatty acid, or modified fatty acid; (2) chemicals with sulfonate or sulfate groups, such as dodecylbenzene sulfonic acid (DDBSA) or its salt, sodium dodecyl sulfate (SDS), sodium lauryl sulfate (SLS), sodium coco sulfate (SCS), etc.; and (3) phosphorous-bearing chemicals, such as sodium tripolyphosphate (STPP), sodium hexametaphosphate (SFMP), trisodium phosphate (TSP), Tetrasodiumpyrophosphate (TSPP), etc. With the improved collector, the separation selectivity and phosphate recovery may be significantly improved.