Based on the ASHRAE Standard 140-2014, this study takes the simulation results of DeST and other simulation software to comprehensively test the accuracy and validity of DeST in calculating building thermal loads and space cooling and heating equipment performance. Special cases were also designed to find out the influencing factors that led to results' differences. It was found that the solar lost through the window, the setting of shading geometry and the mode of inputting surface coefficients can make a big difference to the simulation results. The calculation deviations in most ASHRAE-140 cases are within 10%, which indicate the accuracy of DeST in building energy simulation.