In this work we present the ED (economic dispatch) problem in mixed AC-DC (alternative currant- direct current) systems based on the calculation of PF (power flow) and its equivalent losses matrix. The procedure starts by the calculation of the PF for AC-DC system, then the calculation of the losses matrix. After that, we calculate the ED problem by an optimization method called IPM (interior point method). The active powers founded by the ED problem, will be used for the recalculation of the new PF. The process will be repeated until the convergence of the results. At the end several simulations will be set in 14 bus system, contains five production units, with and without DC links.-In this work we present the ED (economic dispatch) problem in mixed AC-DC (alternative currant- direct current) systems based on the calculation of PF (power flow) and its equivalent losses matrix. The procedure starts by the calculation of the PF for AC-DC system, then the calculation of the losses matrix. After that, we calculate the ED problem by an optimization method called IPM (interior point method). The active powers founded by the ED problem, will be used for the recalculation of the new PF. The process will be repeated until the convergence of the results. At the end　several simulations will be set in 14 bus system, contains five production units, with and without DC links.