In this study, a reinforcement learning based power assisted method is proposed for pedelec, which is a Light Electric Vehicle (LEV) driven by a human's pedal force and electric motor. The proposed method adaptively chooses appropriate assisted power according to the environmental changes. By adaptively adjusting the assisted power after learning for pedelec, not only energy utilization is improved but comfort of riding for pedalist is also satisfied. Simulations of the proposed method on pedelec powered by battery are performed. Experimental results demonstrate that the proposed method satisfies the requirement of comfort of riding and achieve better energy utilization by comparing with other conventional power assisted methods.