For the difficulties of achieving accurate clock synchronization in hanwave-in-the-loop network simulation testing using Precise Time Protocol (PTP), the performance of the simulation system of PTP in the face of slave clock frequency drift was studied. The system model and clock model of PTP under hanwave-in-the-loop network environment were established, the time delay estimation error for the master clock estimated by Slave_n in unidirectional transmission line was analytically derived. It turned out that each drifting slave led to an additive error of identical structure, these error terms got added both in the drifting slave and its successor, and were then percolated down the line together with the previous accumulated error. Based on this, various network simulation scenarios were designed for verification, analysis and testing. The simulation results show that if only one slave clock drifts, the error at the end of the line is slight; but when all the slave clocks drift, synchronization error is more than 10 times larger, and the same relationship holds for the master versus all slaves drifting, which makes a serious impact on the system synchronization accuracy. The research provides an important reference for the clock deployment strategy in hanwave-in-the-loop network simulation.