Abstract: Impinger is an aerosol sampling device based on inertial separation. In order to evaluate the physical sampling efficiency of impinger, a reference sampler evaluation method based on liquid optical particle counter was proposed. The physical sampling efficiency of a domestic product in the particle size range of 1μm-10 μm was evaluated by this method and the upstream and downstream evaluation method. The test result shows that the sampling efficiency evaluate by the two methods are basically consistent in the 1 μm-6.8 μm range, and the sampling efficiency increases with the increase of particle size. The sampling efficiency reaches 80.68% at 6.8 μm with up-downstream method and 78.70% with reference sampler method. In the 6.8μm-10μm range, the evaluation results of the up-downstream method increased continuously, reaching more than 88% at 10 μm, while the evaluation results of the reference sampler method showed a downward trend, decreasing to less than 28% at 10 μm. The evaluation result of the reference sampler method is more in line with the actual situation, and it is recommended to use the reference sampler method for the evaluation of large size particles. Comparing the physical sampling efficiency of water and ethanol as the sampling medium, it is found that when the sampling medium and particles have good wettability, the evaluation result of the reference sampler method will be improved, while the evaluation result of the up-downstream method is basically not affected, indicating that the reference sampler method should consider the wettability of the sampling medium and particles to obtain accurate evaluation results. This study provides a reference for evaluating the physical sampling efficiency of impinger.