Abstract : Nowadays, automotive electricity generators are claw-pole alternators. They have a good power-to-weight ratio and an attractive cost, but their efficiency is low. As on board electricity demand is rising, electricity generation impact on fuel consumption is no more negligible. Our work aims therefore at making a model of claw-pole alternator behavior, according to building parameters, in order to use it in an optimization software to increase efficiency and / or power-to-weight ratio. Our claw-pole alternator model is built using a magnetic equivalent circuit, with analytical expressions of the reluctances. In order to compute the alternator output current, the magnetic equivalent circuit is linked with an analytical model of the rectifier bridge. Then analytical model of alternator losses is presented. Next, this model is used with a gradient constrained optimization software. It leads to solutions set that satisfy product specifications, handling a high number of variable parameters (18 building parameters are optimized together). This approach presents different possible evolutions to improve claw-pole alternator efficiency. Finally, a multi objectives optimization method is used to find the best compromise between high efficiency and high power-to-weight ratio.