The nearly 180° steering path and variable strength of 1214 Typhoon "Tembin" make its forecasting more difficult. Relied on the NCEP reanalysis data, invertibility principle of potential vorticity combined with synoptic situation analysis, as well as assumption of Rankine vortex, the abnomal track of "Tembin" is investigated through isentropic potential vorticity diagnostic analysis and potential vorticity inversion. Results show that Fujiwara effect, which means the eastward shift of the upper trough and the stagnation of the subtropical high, is the main reason for the abnormal turning. The process of "Bolaven" moving to the northwest direction influences the westward extension of subtropical high. "Tembin" would be affected more obviously by binary interaction compared to "Bolaven". According to the influence on the continental high pressure, the upper trough has further indirect impact on "Tembin" movement. Counterclockwise cross-spinning is the key factor for abnomal path of "Tembin". This type of abnormal path formation is the result of the interaction between large-scale environmental field and Fujiwara effect.