In order to make up for the lack of a single energy source for existing electric vehicles. Using battery and ultracapacitor hybrid energy system, battery as main energy source, ultracapacitor as auxiliary energy source. Optimized its parameters through vehicle dynamic performance, driving range, braking energy recovery and other constraints. Considering relationship between ultracapacitor voltage and its capacity and efficiency, formulated fuzzy control strategy based on ultracapacitor voltage, battery SOC and vehicle power requirements. In order to avoid the incompleteness of the single cycle simulation conclusion, multiple cycles of simulation are performed in the UDDS road condition until the discharge end. The results show that the parameter matching method and fuzzy logic control strategy of battery-ultracapacitor hybrid energy system can meet the demand for energy and power of pure electric vehicle during complete discharge running cycle,effectively recycle and utilize regenerative braking energy, improve energy system efficiency, improve vehicle power performance and economic performance, play a role in extending battery life.