The open-loop mode resonance theory is an important theoretical achievement to explain the mechanism of system instability caused by the grid connection of permanent magnet synchronous generator (PMSG), but the determination of the resonance risk of open-loop mode based on the black box measurement model is rarely introduced in its theoretical research. In the past, the determination of resonance risk in open-loop mode relied on accurate parameterization models. However, in practical applications, it is often difficult to obtain the detailed parameters of PMSG, so it is impossible to establish an accurate parameterization model of the system. Therefore, a method for determining the risk of open-loop mode resonance based on the measurement model is proposed in this paper. Firstly, the PMSG to be studied is regarded as a black box model, and its frequency response is measured by injecting voltage disturbance using frequency sweep method. The impedance transfer function matrix is obtained after fitting the frequency response of the measurement model by vector fitting technology, which is transformed into a time-domain state-space model and connected to the closed-loop system. Then, the general analysis method of open-loop mode resonance based on the measurement model is used to determine the system instability risk. Finally, a simulation example is used to demonstrate the analysis and determination process of resonance risk in open-loop mode. The results show that the resonance risk of open-loop mode can also be determined based on the measurement model. The proposed method does not need to obtain the detailed internal parameters of the PMSG, and has high engineering practicability.