The purposes of this paper are to analyze the category and the reasons for the time-lag effects of urban land market regulations,and explore the impacts of the time-lag effect on the commercial housing supply.Method of polynomial distribution lag model was employed.The results indicate there exists some characters of the time-lag effects of land supply regulations,which are:(1)effect is significant;(2)long-term continuity;(3)with influences on market operation;(4)playing both positive and negative roles.It is concluded that the time-lag effect and its transmission mechanism are closely related to the expectation of the market actors and other factors,therefore the corresponding adjustments should be made to current urban land market regulations.