In this thesis, We propose two power saving strategy in wireless sensor networks with multi-packet reception and slotted ALOHA is as a systematic model. We concentrate on the case in which the packet arrival process is Bernoulli and the maximum queue is 1.This thesis first simulate results and to compare with the analytical results of pervious thesis. Traditional slotted ALOHA only have transmit and idle state. In this thesis, add a sleep state to decrease the energy consumption, and according to different strategy propose two different methods. This two methods decide to the sleep time and the retransmission probability to achieve the energy-efficient. At last we will use the simulation result to show the performance of our power saving strategy.