A surface mesoanalysis system has been developed to take advantage of automated surface observing system (ASOS) data that are becoming available in real-time for operational nowcasting.It is designed using Barnes schemes of successive corrections and the bandpass filtering technique, and many mesoanalysis products can be displayed by MICAPS system, it is useful for forecaster to analysis and correct the prediction for the nowcasting of severe weather. As a verification study examples, a severe thunderstorm attacked Shandong province on 28 Apr., 2006 is analyzed, the results indicate that the system has good effect in watching the real-time evolution of meso-scale weather features, but the quality control of ASOS is key and difficult questions. The discusses about how to make nowcasting using ASOS, radar and satellite data are given.