The invention discloses a precise control method for the growth starting temperature of a mercury cadmium telluride liquid phase epitaxy system. The method is characterized by comprising the following steps of: adding a secondary cooling process before pre-growing to guarantee that the pre-growth temperature is higher than the growth temperature and within an allowed range; performing once trial short-time growth before the temperature of mother liquor approaches the starting growth temperature to be controlled; and determining the time to start to grow formally according to the variation of the temperature of a sample rack. The method has the advantages that: the starting growth temperature of the mercury cadmium telluride liquid phase epitaxy system can be controlled precisely, so the quality of the epitaxy layer and the finished product rate of epitaxy cannot be affected by an excessive height of a growing component caused by the over back-melting of a mercury cadmium telluride substrate and dramatic growth of the sample rack and the surface of the substrate caused by the over-low starting growth temperature.