Financial constraint refers to the situation under which the firm cannot obtain the required external funds to achieve the optimal investment. In this study, I construct a theoretical financial constraint model based on informativeness of accounting earnings to explore the relationship between the informativeness of accounting earnings and investment cash flow sensitivity (a measure for the degree of financial constraints). Using the regime switching regression model, this study empirically tests the proposition derived from the above theoretical financial constraint model. The empirical result indicates that investment cash flow sensitivity is irrelevant to the informativeness of accounting earnings itself for a firm without financial constraint. However, when a firms is financially constrained, the investment cash flow sensitivity decreases as the informativeness of accounting earnings increases. In addition, the evidence also indicates that firms with higher growth opportunity have higher financial constraints. The important implication of this study to financial management is that management should increase the informativeness of accounting earnings to enhance the investment upper limit through financing multiplier, so that the firm would not suffer financial constraints and thus affect its growth.