Abstract: In order to decrease greenhouse energy cost in winter in Yangtze River Delta, design method of open-loop surface water source heat pump system (SWSHPS) for greenhouse heating was presented based on greenhouse heat load prediction technology. Combined various environmental factors of greenhouse with actual operation of greenhouse, thermal balance prediction model was built. Greenhouse heating loads were numerically simulated under 8 kinds of environmental conditions using Matlab/simulink and the greenhouse energy cost was calculated under the conditions of different covering materials and opening or closing thermal screen. The conclusion that when the outside air temperature was 0℃,the greenhouse covered by glass coating with ATO (antimony doped tin oxide) could decrease energy consumption 23% than greenhouse covered with conventional float glass, and at night the greenhouse with the opening internal thermal screens of the roofs could reduce energy consumption 22% than the greenhouse with closing them was arrived at based on model calculation. And then the heating experiments of greenhouse were conducted in winter. The results showed that distribution of air temperature was uniform in greenhouse, temperature met the needs of greenhouse environment, and average COP (coefficient of performance) value for system in January was 2.3. Greenhouse heating design method of SWSHPS based on thermal balance prediction model is reliable.