Abstract: Charging for electric tricycle by solar energy has high engineering values. Based on the perturb-and-observe algorithm（P＆O algorithm） and interleaving parallel technology, this article designed a step-up boost converter for electric tricycle. The charging method for lithium battery of electric tricycle is constant-current and constant-voltage. A two-parallel interleaved Boost booster circuit and its charging algorithm were completed and simulated, whose simulation discloses that the system is stable. In the constant-current charging phase of lithium battery, the photovoltaic P＆O algorithm simulation shows that under the same disturbance step, the converter has lower current output ripple and power output oscillation for photovoltaic battery. The indoor charging result shows that under the constant-voltage limitary-current charging algorithm, the converter has better output properties. The outdoor charging result shows that in the constant-current charging stage, the photovoltaic panel always works around 30 V for the maximum power point. Furthermore, its charging efficiency can be above 95% in most load ranges.