Release agents are indispensable auxiliary agents in the high-pressure die casting production process. Improper selection of the release agent will cause surface quality problems and defects in the casting. Therefore, it is necessary to conduct appropriate performance testing of the release agent prior to its machine application. Two commercial water-based release agents (type A and type B) commonly used in aluminium alloy die-casting production enterprises were selected to study the testing methods for typical performance indicators of release agents. Through viscosity tests, particle size tests, thermogravimetric tests, gas chromatography-mass spectrometry tests, contact angle and surface tension tests, and room temperature stability tests, the demolding performance, thermal stability, adhesion performance and room temperature stability of the two release agents were comprehensively evaluated and analysed. The results show that the type A release agent has better thermal stability and demolding performance than the type B release agent does. Moreover, the gas volatilization of the type A release agent is lower, effectively avoiding the generation of bubble defects in die castings.