The service processes of typhoon Fengshen are summarized when the performance of numerical weather prediction is disabled and the typhoon forecasting track is deviated to easterly. At that time, prompt revisions are made to typhoon forecasting track based on the nice changes of weather conditions. During the services, 1500 people working on maritime oil platforms are evacuated safely. Therefore, casualty and economic loss are avoided because of our high responsibility and good professional ethics. The results show that: (1) typhoon Fengshen turns westwards because of strong convection on the west side of Fengshen, negative pressure variety at the ground level, plus vorticity center at the middlelevel, and plus divergence at the highlevel . At the same time, the beltshaped blackbody area on the north side of “Fengshen” on cloud chart is also favourable to its turning westwards. (2) At 500 hPa, twice turnings northwards are caused by the low pressure circulation centre on the southwest side of typhoon and the high pressure belt on the northeast side successively.