This paper presents a new approach based on the combination of the Particle Swarm Optimization and the gradient method to solve the unit commitment (UC) problem. The proposed strategy optimizes the combination of production units operations and determines the appropriate operational scheduling of each production units to satisfy the expected consumption during a well specific duration. Each production unit is conducted to constraints that render this problem complex, combinatorial and nonlinear. The resolution of the UC Problem is conducted to several constraints that take into account the minimum up and minimum down time constraints, start-up cost and spinning reserve. The adopted approach was applied to an IEEE electrical network 14 buses containing 5 production units and the simulation results have clearly proven that the Gradient-PSO method was very competent in optimizing the UC problem in comparison to other existing methods.