Unifying the cooling capacity measurement result has a fundamental effect on energy conservation and emission reduction in airconditioner industry. The waterenthalpy method cooling capacity source could be applied in the calibration of cooling capacity measuring apparatus; it could supply a cooling capacity that is measurable and controllable. In this research, the principle of the waterenthalpy method, which reduces the number of measuring parameters, was illustrated first. Then, the physical structure of the source was designed and developed, and the source was experimentally investigated with a balanced ambient roomtype calorimeter. The experiment results show that the maximum relative difference of cooling capacity between the source and the calorimeter is less than ±0.7%. Finally, the uncertainty evaluation process and result of the cooling capacity output of the source are given in detail. The evaluation results show that the repeatability of the source is 11.4 W; as the cooling capacity increases from 1 660.8 to 5 810.4 W, the combined standard uncertainty increases form 12.3 to 18.2 W, and the relative expanded uncertainty decreases from 1.5%（k=2） to 0.6%（k=2）. With the waterenthalpy method the traceability of cooling capacity source is achieved for the first time from the perspective of metrology, the cooling capacity could be traced to temperature, pressure, flow rate and electric power, and the source apparatus could be used as standard cooling capacity source in calibration.