By using the GSI (Gridpoint Statistical Interpolation) assimilation system developed by NCEP (National Centers for Environmental Prediction) and the global spectrum prediction model of GSM (Global Spectral Model) as the cyclic assimilation system,the thirteenth typhoon in 2017 was selected for a case study.The two assimilation schemes of all sky and clear sky were used to make assimilation comparison test on AMSU-A (The Advanced Microwave Sounding Unit-A) radiance observation,and the authors implemented 5-day forecast on typhoon "HATO" to study the impact of AMSU-A full-sky radiance assimilation on the development of typhoon HATO.The results showed that errors in typhoon path,typhoon center pressure and typhoon's maximum wind speed predicted by the all-sky assimilation scheme were smaller than those by the clear-sky assimilation scheme.The full-sky assimilation scheme was more accurate in the simulation of typhoon HATO's life cycle,and it was closer to the lowest pressure of the best path of the typhoon released by China Meteorological Administration.The result forecasted by the clear sky assimilation scheme was weaker and the typhoon intensity at its mature stage could not be predicted.The full-sky assimilation scheme could increase the thick cloud coverage area of the low-level passage.The amount of radiance data assimilation increased by 10% of the total amount of AMSUA assimilation observations,and thereby improved the thermal field structure of the weather system in the marine area.