The invention relates to a reverse flotation collector of carbonate phosphate ores and a preparation method thereof. The collector is essentially composed of the following raw materials by weight proportion: 0.5-0.8 part of acidified raw bran oil, 0.5-0.2 part of acidified soy oil, 0.01-0.1 part of foamer which takes semi-finished products after saponification as benchmark. The preparation methodof the collector is that: the mixture of the acidified raw bran oil and the acidified soy oil is taken as raw material, which is heated to 80-100 DEG C, added with soda lye and stirred for saponification, the pH value is controlled between 7 to 8, and then the foamer is added into the mixture to obtain finished products. The collector has the advantages of strong collecting capability, high selectivity, small dosage and low temperature resistance, etc., and is suitable for the ore dressing production of carbonate phosphate ores and various phosphorus ores; even when the grade of carbonate phosphate ores is reduced to 17%, the quality of the produced phosphate concentrate still can meet qualification requirements; in addition, the invention has simple preparation technique, easy operation,high recover rate of ore concentrate, low content of MgO in ore concentrate and low ore dressing cost.