This study takes Korean listed companies as the research object, and empirically analyzes the impact of cash holdings on Firm value from three perspectives: all enterprises, manufacturing industry and non manufacturing industry. The enterprise value is measured by the Tobin's Q. And the independent variable is cash flow and the square value of cash flow. Control variables consist of company size, debt ratios, cash flow of investment activities, Return on assets and dummy variables .The main results of this study are as follows. Firm value Tobin's Q and level of cash flow show a significant (+) linear relationship and show a negative (-) correlation between firm value and the square of cash flow. There is a U-shaped non-linear relationship between cash holding level and firm value. With the increase of cash holdings, the value of the company will rise, but beyond a reasonable range, the continuous increase of cash holdings would reduce the firm values.