The state transfer of nS Rydberg atoms induced by external pulsed electric field has been investigated. Cold nS Rydberg atoms are prepared by the two-photon transition and the selective field-ionization method is used to detect the Rydberg atoms and "P" state due to the state mixing. The avoided crossing of nS and (n-4) manifold is studied and the dependence of the state transfer rate on the strength of pulsed field is obtained. Experimental result is interpreted by using Stark effect of electric field and it shows consistency between experiment and calculation.