In-depth analysis of the conventional battery charging method and charging technical requirements of lead-acid battery in small wind power system, designed a three-stage intelligent charger based on SG3525A, its main circuit using the push-pull isolation convert structure, the charge strategy using three-stage approach of constant current, constant voltage and trickle charge to achieve at different stages of battery charging requirements. The experiment results show that: The charger can adapt to a wide range voltage of charging request, and can achieve real-time monitoring charge state and status display, and has over-voltage, over-current protection.