On the basis of optimizing WRF ensemble square-root filter assimilation system with two-way nesting forecasting scheme and radar data quality control scheme,which also integrates multi-physics ensemble integral scheme,a new ensemble initial perturbation scheme with perturbed potential and stream functions is introduced.This new scheme has smaller perturbed scale and more obvious physical meaning.With direct assimilation of Doppler radar data on the landfalling of typhoon Saomai,this paper compares the impacts of the new perturbation scheme,the background error covariance random perturbation scheme and the whole space random perturbation scheme on the ensemble filter assimilation.Result shows that all three initial perturbation schemes can improve typhoon structure,but the assimilation effect of the new scheme is more distinct due to smaller scale and better physical structure,which can improve the forecasting quality of typhoon track,center minimum pressure,maximum wind speed and precipitation.