The invention discloses a process for preparing cadmium sulfide quantum dots by a low temperature two-phase synthesis method. The process is as follows: a cadmium source is dissolved in oleylamine at room temperature, oleic acid is added for dilution to prepare a cadmium solution as an oil phase; the cadmium source is one of cadmium chloride, cadmium sulfate and cadmium nitrate, the volume ratio of oleylamine to oleic acid is 1:4; sublimated sulfur powder is ultrasonically dissolved in dimethyl sulfoxide containing tri-n-octylphosphine at room temperature to prepare a sulfur solution, or a sulfur compound is directly dissolved in the dimethyl sulfoxide containing the tri-n-octylphosphine to prepare a sulfur solution; the sublimated sulfur powder or the sulfur compound is used as a sulfur source, the sulfur compound is thiourea or sodium sulfide, the tri-n-octylphosphine is used as a wrapping agent, the molar ratio of sulfur source to wrapping agent is 2:1; the cadmium solution is mixed with the sulfur solution for reaction for 30 minutes under the condition of water bath at 70 DEG C, and the cadmium sulfide quantum dots are produced in the oil phase. The process has the advantages of wide raw material sources and low reaction temperature, the prepared cadmium sulfide quantum dots are uniform in particle size and narrow in size distribution, the absorption peak position can be adjusted between 396 to 445 nm, and the fluorescence is strong.