The studies of using surplus energy in Chinese solar greenhouses (CSGs) are the background to conducting the research for this paper. This study presents a novel water heat accumulator below the north roof. The experiment analysis method investigated the possibility of heat collection and release below the north roof. And its independent heat collection efficiency can reach 0.21 W·m−2. The materials, forms, and coverings of the collector panels have been optimally explored in the experiment. The experimental results show that the polyethylene bag-type collector is the best. The heat storage and release are 11.01% and 19.56% higher, respectively. The average increase in thermal resistance ranges from 0.009 to 0.018 K·W−1 by the influence of covering. The significant finding is that the correlation coefficient between water and air temperature was between 0.83 and 0.85, much greater than the correlation between water temperature and radiation. This paper aims to provide a new perspective on the active heat storage and release system in Chinese solar greenhouses.