Abstract: This study presents the optimisation of a photovoltaic water pumping system using Maximum Power Point Tracking Technique (MPPT). The optimisation suspends to reference optimal voltage. This technique is developed to assure the optimum chopping ratio of Back-Boost converter. It was experienced in photovoltaic water pumping system in order to optimise its global efficiency and to increase its power instead of linking it directly or using the complex MPPT technique. And it keeps its efficacy at high temperature and with guaranteeing its practical execution simply and easily.