Changes in the East Asian summer circulation have great impacts on summer rainfall in China. It is necessary to better understand the forecasting capacity of seasonal forecast models. In this study, we evaluated the capacity of seasonal forecast models for the forecast of the intensity of East Asian Summer Monsoon (EASM) and Western Pacific Subtropical High (WPSH) in the summer based on the NCEP/NCAR reanalysis and simulations for 1991-2013 from three seasonal forecast models, i.e. CFS V2, BCC_CSM V2 and MRI-CGCM. These models are from National Centers for Environmental Prediction (NCEP), National Climate Center (NCC) and Tokyo Climate Center (TCC) respectively. To illustrate the origin of forecast errors, we analyzed responses of the EASM and WPSH to tropical sea surface temperature (SST) anomaly in these models and impacts of ENSO events on the forecast of the EASM and WPSH. Analysis results indicated that the forecast skills for the EASM and WPSH were high in all models, while those of the TCC model are relatively low. An anomalous cyclone was simulated over western North Pacific, resulting in stronger EASM and weaker WPSH compared to that of observations in all models. Meanwhile, the annual variability of the EASM and WPSH was weaker than that of observations. Characteristic responses of the EASM and WPSH to tropical SST anomaly and its seasonal evolution were close to those of observations in all models. The response of the EASM to the preceding tropical Pacific Ocean SST anomaly and the preceding and simultaneous tropical Indian Ocean SST anomaly in NCEP model and TCC model were stronger than those in observations, and the responses of the EASM to the preceding and simultaneous tropical Pacific Ocean SST anomaly in NCC model were obviously stronger than those in observations. Besides, the responses of the WPSH to the preceding and simultaneous SST anomalies over tropical Pacific Ocean, tropical Indian Ocean and tropical Atlantic Ocean were obviously stronger in all the models than those in observations. The mean absolute errors (MAE) of the EASM and WPSH forecasted by the three models in ENSO events overall were much smaller than those in normal years. The MAEs of the EASM and WPSH forecast by NCEP model and NCC model in La Niña events were close to that in El Niño events, while The MAEs of EASM and WPSH forecasted by TCC in El Niño events were much higher than that in La Niña events. This result also indicated that ENSO event was an important source of forecast for the East Asian summer circulation.