Price is the core of the real estate market, due to this view, the research of the real estate market decision theory can shift into the research of the influencing factors on prices. This paper chooses the influencing factors of real estate price from market environment of real estate, market demand and supply. Introducing the method of grey correlative degree analysis, the paper takes Xi'an as an example, and analyzes those factors impacting on the real estate price. The paper enumerates the importance of factors, ranging from the most to the least important in their order, namely Transactions Price Indices of Land, General Residents Consumer Price Index, Price Indices of Construction and Installation Projects, Renting Price Indices of Real Estate, etc.