This article examines the liquidity-investment relation of Chinese SMEs in comparison to large firms, and specifically focuses on the exogenous IPO event to observe how the responses of firm investment to cash flow change subsequent to the IPO. We find that the sensitivity of fixed investment to cash flow varies with firm size, and the over-reliance on internal funds by SMEs has reduced more prominently after the IPO than their larger counterparts, providing new evidence that liquidity constraints of investment are not constant in the same firm but shift along the life cycle. Our results strongly suggest that other financial resources to cover the cash flow shortfalls resulting from timing differences between the operating and investment cycles need to be considered in the examined relation and previous studies may have underestimated the impact of liquidity constraints on firm investment.