This paper puts forward a new kind of under-floor electric heating system with phase change material (PCM) plates with ductless air supply. Different from conventional PCM, shape-stabilized PCM can keep the shape unchanged during phase change process. Therefore, the PCM leakage danger can be avoided. The system can charge heat by using cheap nighttime electricity and discharge the heat stored at daytime, and can control the heat flow rate by ductless air supply to improve thermal comfort degree and save energy. A prototype room with this system was set up and the temperatures of the system and the indoor air were measured, and its effect analyzed. The results show that the system can perform well. The temperature of the PCM plate upper surface can be kept near the phase transition temperature during the whole day and a lot of off-peak period electricity can be used for space heating instead of using peak period electricity, which obviously lowers the electricity costs.