Abstract: The heaviest rainfall over 61 years hit Beijing on 21-22 July 2012. Characterized by its great rainfall amount and intensity, wide range, and high impact, this record-breaking severe rainfall caused dozens of deaths and extensive damage. Despite seeming typical in terms of synoptic conditions, the operational forecasts underestimated the precipitation amount and were later as to predicting the rainfall start time. To gain a better understanding of the performance of mesoscale models, verification of high-resolution forecasts and analyses from the WRF-based BJ-RUC v2.0 model with a horizontal grid spacing of 3 km is carried out. The results show that in this case water vapor is very rich and a quasi-linear precipitation system produces a rather concentrated rain area. Moreover, the model forecasts are first verified by using statistically the Equitable Threat Score (ETS) and BIAS score.The BJ-RUC v2.0 forecasts under-predict the rainfall with a southwestward displacement error and time delay of the extreme precipitation. Further quantitative analysis of the contiguous rain area (CRA) method indicates that major forecast errors for total precipitation (>5 mm/h) are due to inaccurate precipitation location and pattern, while forecast errors for severe rain (>20 mm/h) mainly come from precipitation intensity forecasts. Finally, the possible causes for the poor performance are discussed through diagnosing large-scale circulation and physical parameters (water vapor condition and instability conditions) based on the BJ-RUC v2.0 model outputs.