The combination of floor cooling and displacement ventilation is a common method, which was used in the engineering application. Displacement ventilation not only offers fresh air for room's sanitary requirement, but also prevents the floor surface from condensation. This paper analyzed the floor cooling and displacement ventilation in the experiment and the theory, which indicates that the displacement venti-lation can not solve the condensation problem but reduce the condensation in some degree. It comes to the conclusion that the condition point of the dry fresh air in displacement ventilation is relation to the indoor and outdoor humidity environment, and real - time monitoring can prevent the surface from condensation.