One of the focal points in analyzing China’s economic situation at current stage is the serious decline in the growth of private investment. This article investigates such situation in the following three aspects：private investment growth rate；contrasts between private investment growth rate and the national investment growth rate；the proportion that private investment is accounted for due to the total investment nationally. There are various reasons for causing the serious decline in private investment growth. This paper points out that the most important factor is the profitable investment does not meet the expected target and the enterprises lost hope on making more profit. This paper analyses four types of enterprise profit expectations：classical expectation；extrapolation expectation；adaptive expectation and rational expectation. Finally，the paper suggests and indicates that to create a favorable macroeconomic environment by aiming to benefit the profit expectation of the enterprises is the most sufficient and necessary condition in order to encourage the growth of private investment.