The present application provides a control method and device for an air conditioning unit, the method including: obtaining a return air temperature, a condensation temperature, an evaporation temperature, compressor parameters, and fan parameters of the air conditioning unit; determining a preset evaporation temperature according to the return air temperature, the condonation temperature, the evaporation temperature, the compressor parameters, the fan parameters, a compressor power curve, and a fan power curve, wherein the sum of a compressor power and a fan power is minimized at the preset evaporation temperature; determining a preset compressor frequency and a preset fan frequency corresponding to the preset evaporation temperature according to the compressor power curve and the fan power curve; controlling a compressor according to the preset compressor frequency; and controlling a fan according to the preset fan frequency.