The large eddy simulation (LES) is used to resolve the flow structure in the cavitating turbulent flow around the Clark-Y hydrofoil coupled with a homogeneous cavitation model. A new method is proposed in this paper to calculate the LES error of the time-averaged streamwise velocity for the LES verification and validation (V&V). From the instantaneous cavity patterns, it is demonstrated that the predicted results agree fairly well with the experimental data. With this new proposed method, the LES errors can be easily and effectively calculated with a limited mesh number, and the method might be used in the other applications of the LES V&V. Results of the LES errors obtained by the new method show that the relatively steady flow can be simulated with small errors, while the complex flow structures at the cavity shedding region might lead to an increase of errors in the LES modeling. In addition, the distributions of the resolved Reynolds stresses are used to estimate the influences of the cavitation on the turbulent fluctuations. Results indicate that the turbulent fluctuations for the cavitating flow are much larger in magnitude as compared to the cases without cavitation.