In order to test sensitivity of radar data in different typhoon radial distance area, radar data is divided into three parts to be assimilated individually. Result of typhoon Mujigae(1522) simulation shows that radar observations within 100km from the typhoon center are dominate in the assimilation of typhoon track, intensity and structure simulation, which just account for about 20% of the total observations. Moreover, it makes no obvious difference on the typhoons’ track, intensity and structure errors for all radar data assimilated or those only within 100km. The simulated typhoon structure is somewhat modified by cycling assimilating observations in 100-200 km or out of 200 km from typhoon center. Experiments for typhoon Rammasun and Meranti also show that radar observations located close to the typhoon center is dominant in typhoons intensity and structure. Since only assimilating inner core radar data can reduce computing time to 1/3 of all data with somewhat the same assimilation result. Efficiency of radar assimilation can be much improved by this radar assimilating strategy, and it can provide operational guidance for typhoon real-time data assimilation and prediction work.