The invention discloses a test system and method for the cooling performance of a microscale liquid cooler. The test system for the cooling performance of the microscale liquid cooler comprises the microscale liquid cooler, a heating device, a temperature measurement system, a cooling liquid circulator, a metering pump and a diverter. According to the test system, on one hand, high reliability, high accuracy and high precision of a micro-fluid division control technology are utilized, and the temperature, the flow and the pressure of the cooling liquid are accurately controlled step by step through the cooling liquid circulator, the metering pump and the diverter, so as to achieve accurate control of low-flow or extra-low flow cooling liquid; on the other hand, a surface temperature field of the heating device is monitored in real time by adopting an advanced infrared thermal imaging technology; visual observation of a working temperature field of a microscale device is achieved. By adopting the test system, the accuracy, the precision and the reliability of measurement of the cooling performance of the microscale liquid cooler are greatly improved; the test system is especially suitable for test of the cooling performances of the microscale liquid coolers for aerospace, information communication, transportation and medical treatment, automatic control, consumer electronics and the like.