Abstract: The renewable energy inertia response is gradually becoming a new requirement of grid connection regulations and a new product in the auxiliary service market. The testing of inertia response performance and the evaluation of inertia time constant can help meet the corresponding requirements of grid connection regulations and clear the economic benefits of auxiliary service products. However, the evaluation method for the inertia time constant is not involved in the test standard of inertia response performance. Therefore, this paper proposes an evaluation method for the inertia time constant of renewable energy based on delay compensation. Firstly, the rate of change of frequency and the frequency offset that may exist in the system are generated based on the power grid simulator, and the time nodes for full dynamic process analysis are reasonably selected according to the key evaluation indicators of inertia to improve the analysis accuracy. Secondly, the active power-frequency delay link in the inertia response process is calculated and compensated to eliminate the evaluation error caused by the delay. Finally, a continuous inertia evaluation algorithm based on the differential synchronous machine swing equation is designed to accurately evaluate the inertia of renewable energy. A renewable energy inertia evaluation experimental environment is built on the RT-LAB semi-physical platform to verify the accuracy of the evaluation results with the proposed algorithm in different delay scenarios.