Abstract: A completely new MPCL(Mechanically Pumped Cooling Loop) system is introduced in this paper and the experimental platform is set up to make MPCL operate more stably and reliably. In the preliminary experiment, when the system is filled with different filling rates, the start-up time and operation performances are studied. The optimal filling rate is obtained. Meanwhile it is concluded that uneven heat source and insufficient drive capability of the pump lead to the poor performance of the system. So the experimental scheme is optimized from these two aspects. The start-up time is shortened and the operation performance of the system is improved after the heat source is optimized. Based on the optimized heat source, the drive capability of mechanical pump is improved. The system has shorter start-up time, lower steady-state temperature and smaller temperature fluctuation. The system can have larger heat load when it operates and has no temperature pulse when the heat load changes. In a word, the heat transfer capability of the system is improved greatly. According to the experiment, the MPCL system can start up smoothly and operate safely. The equivalent heat transfer coefficient of the system gets very large and temperature uniformity of the system is very good. The experimental result has laid foundation for further study.