This paper focuses on the novelty pumpless organic Rankine cycle (ORC) and its choice of working fluids. Based on the selection criteria, the refrigerant of R1233zd(E) is firstly chosen and investigated in the pumpless ORC system. In the system, the feed pump is removed, and the refrigerant flows back and forth between two heat exchangers, which act as the evaporator or condenser, respectively. The impacts of the heating water temperature and loads on the system performance are studied to find out the best operating conditions. The low-grade heat source is simulated by an electric boiler. The temperature of the heat resource ranges from 80 degrees C to 100 degrees C with the interval of 5 degrees C. The temperature of the cooling water inlet is 10 degrees C and is kept constant. The largest average power output is 127 W under the condition of 100 degrees C heating water with nine loads. Because the cycle efficiency with heating steam temperature of 100 degrees C cannot be determined, the highest energy and exergy efficiencies are 3.5% and 17.1%, respectively, for heating water of 95 degrees C with seven loads. The experimental results show that the energy and exergy efficiencies increase with the increase of the heating temperature. The power and current outputs increase when the loads increase under the condition of the constant heating water temperature, whereas the voltage output decreases meanwhile. The generating time increases when the loads increase. This phenomenon is mainly caused by the increasing evaporating pressure and decreasing condensing pressure when the loads increases.