Abstract: Compound formed by single-wall carbon nanotubes (SWNT′s) with ionic liquid (IL).1-butyl-3-methylimidazolium hexafluorophosphate abbreviated as (bmim)PF6 was used to modified on the surface of glass carbon electrode (GCE),which showed better sensitivity than the singly modified SWNT′s/GCE when used as working electrode in the electrocatalytic voltammetric determination of diethylstilbestrol (DES).Based on the results of study on optimum experimental conditions of electrode reaction of the modified electrode,SWNT′s/IL/GCE,a sensitive and rapid method for determination of DES was proposed.Linear relationships between values of peak current and concentration of DES were obtained in 2 intervals ranging from 5.0×10-8 to 1.0×10-6mol·L-1 and from 1.0×10-6-7.5×10-6mol·L-1.Detection limit (3S/N) found for the method was 2.0×10-8mol·L-1.The proposed method was used in the determination of DES in samples of injections and of water.Results found for injection samples were in consistency with the labelled values.On the base of water sample as matrix,test for recovery was made by adding DES standards of 3 different concentrations,values of recovery found were ranged from 96.8% to 103.0%.