Abstract: A detergent for cleaning fins of a condenser/radiator/evaporator has a composition including a surfactant of 0.1%˜55% by weight, an acid substance of 0.1˜50% by weight, and water. The surfactant is made from a halogen or a halide polymerized in an epoxide, and then neutralized with an alkaline substance. The surfactant reacts with the chemical substance of the dirt to remove the dirt from the fins. The acid substance may speed up the reaction. Thus, the detergent of the present invention still may clean the fins in an environment of pH5.0, which is close to the pH value of skin.