For the benefit of environment protection and sustainable economic development especially in western china, to build more hydroelectric power stations is a basic policy of our government. Xiluodu project is the biggest underground hydroelectric power station. which includes 18 power generation units with a capacity more than 12 600 MW. By establish a set of heat and humidity balance equations applying on the Xiluodu project underground workshop with its boundary conditions, this paper has present an one_dimensional heat conduction model to simulate its dynamical heat transfer process. On the purpose of compare deferent design schemes of HVAC system, a package of software for numerical simulation is developed. In this paper,we have also recommend some criteria for the evaluation of HVAC system design schemes. The computation result has show that if utilizing the reservoir water and AC chiller to process the air,combing other anti_humidification technical measures,it will assure the anticipated air quality of underground facilities.