The tropospheric delay is one of the main errors for earth observation and a variety of radio navigation technologies, and the UNB3m model can be used to calculate the zenith tropospheric delay (ZTD) without any real measured meteorological data, which taking the major changes in water vapor profiles with latitude into account, and it widely applied in Wide Area Augmentation System in America. However, there are few researches carried out on the assessment of ZTD from UNB3m model over Asia area. In this study, three years of the ZTD data observed from 56 IGS (International GNSS service) sites distributed in Asia area is used to assess the effectiveness and accuracy of ZTD calculated from UNB3m model. The results are: (1) relative to IGS observed ZTD, the bias and root mean square (RMS) for ZTD calculated from UNB3m model are -0.1 cm and 6.0 cm, respectively. Besides, the bias shows significant periodic characteristics in Asia area. (2) The bias and RMS present seasonal variations, which generally show larger values in summer months. (3) The precision of ZTD calculated from UNB3m model increases with increasing altitude or latitude, and also the bias and RMS show inconsistently in different Asia areas. At last, the best results can be achieved in inland area where presents the mean yearly RMS of 2.4 cm. These results provide a reference for the study of the tropospheric delay correction model and the applications of real-time GNSS navigation and positioning.