Carbon Paste Electrode Modified by silica gel /MWCNTs was manufactured and used for the electrochemical determination of Ascorbic acid (AA) in acetate buffer (pH=5.0) using cyclic, linear sweep voltammetry and square wave voltammetry(CV, LSV, and SWV). The results illustrated that the carbon paste modified electrode give a good response for an electrocatalytic activity toward the oxidation of AA. The electrochemical oxidation of AA at modified carbon paste electrode was diffusion-controlled and irreversible, using the optimum conditions to achieve the lower detection limit 1.07 × 10-8 M, good reproducibility, and high stability. This method has been applied to the determination of AA in orange and lemon fruits, and the recoveries were from 96% to 102%.