Adjusting for occupancy, when controlling an HVAC (Heating, Ventilation, and Air Conditioning) system, is an important way to realize demand-driven control and improve energy efficiency in buildings. Energy simulation is an efficient way to examine the effects of occupancy on a building's energy consumption and a cost-effective and non-intrusive solution to test occupancy-based HVAC control strategies. However, more than one hundred building energy simulation programs are used in research and practice, and large discrepancies exist in simulated results when different simulation programs are used to model the same building under same conditions. This paper evaluates different methods and sequences of coupling occupancy information with building HVAC energy simulation. A systematic review is conducted to analyze five energy simulation programs, including DOE-2, EnergyPlus, IES-VE, ESP-r, and TRNSYS, from the following five perspectives of heat transfer and balance, load calculation, occupancy-HVAC system connection, HVAC system modeling, and HVAC system simulation process.