In recent years,the overheating of real estate investment and excessive increase of house price has already become the focus of the attention of the society,the hot topic of the academic circle and an important part of the government’s marcroconomic work. But the formation of Real Eatate Market in our country is reletively late,and have not form an entirely complete theory and method to the Real Eatete Price.At present,the study on the Real Eatate Price is richful and focus on the study of the supply - demand relationship that affects the Real Eatate Price.This paper believed that: First,the quality of uncompletely comptete of the Real Eatete Market,making the Real Eatete Price is not entirely decided by the supply - demand relationship.Second ,the change and development of cost ,which takes a great part of Real Eatete Price, have directly effect on Real Eatete Price.Third, with the increased intensity of government policies to the Real Eatete Market, that making policy factor have also become another important factor that put effcet on the Real Estate Price.So,the study of Real Eatate Price join the three factor: cost, supply-demand relationship and the government policy together.Based on this view,this paper takeing the main city of Xi’an as the research areal, chosing the price of Commercial Dwelling House(CDH)which is most concerned by the community as the target,take the basic theory of the price of CDH as the basement.After analysing the status quo of the market of CDH,from three perspectives:cost, supply-demand relationship and the government policy.to study their effect to the price of CDH.Study the detail constitution and the development of cost of CDH in Xi’an,analysing the changes of the cost that taking effect to the price of CDH, clarify the changes of the price of CDH from the cause.Finally, choosing Artificial Neural Network, from the cost perspective and the supply-demand relationship respectively, build Back Propagation( BP )neural network forecasting model of the price of CDH and pridict the house price of the following three years.Then, analysing the pridict result from the perspective of the policy. This paper first time provide that study Real Eatate Price from cost, supply-demand relationship and the government policy,overcome the limitation of the study just fronm the supply-demand relationship.Provide new vision to study Real Eatate Price.The prediction model in this paper is proved have high maneuverability and high precision and provide an effective tool to accurately analysis and forecast the Real Estate Price.