The important problem of using passive filters remains in the determination of their sizes, which meets standard levels of harmonic distortion with the minimum of cost. Many multi-objective optimization methods aiming at reducing cost an Improving electrical power quality have been used. The purpose of this paper is therefore, to show the application of ANT COLONY OPTIMIZATION (ACO) to design the passive filters sizing worry in an electric network affected by harmonic disturbances. In this work, the objective function to be minimized is the value of current harmonic distortion and passive filters cost, these passive filters are simultaneously connected in parallel with (FAP) in load side in order to achieve the percentage of (SAPF) apparent power (SF) compared to (Load) apparent power (SL) Limited between 14% and 16% and become very reasonable. The studies have been accomplished using simulation with the MATLAB-Simulink. The results show That (SHAPF) is more effective than (SAPF), and has lower cost.