In order to measure the dynamic burn rate of solid propellants under erosive combustion conditions, an erosive burn rate testing system was designed. This testing system is based on a transparent-window engine and includes pressure sensors, high-speed cameras, and a data acquisition system. The transparent-window engine is used to create high-temperature and high-pressure transverse gas flow conditions for the propellant sample to produce erosive combustion, and the high-speed camera is used to capture the process of combustion recession on the sample surface. A certain standardized nitroglycerin propellant was used as the test subject, and ground hot fire tests for erosive combustion were carried out. Combined with CFD numerical research, the reliability of the constructed erosive burn rate testing method and mathematical model was analyzed and verified. The results show that this erosive combustion testing method also has a series of prominent advantages such as low cost and high efficiency, capable of obtaining multiple sets of data in a single test, and suitable for rapid measurement of erosive burn rates of various solid propellants.