The solubility of a drug in supercritical carbon dioxide (ScCO2) is an important parameter for preparing the controlled release drug by supercritical fluid technology. In this work, a test technique of the flowing solubility is developed, and the test apparatus is set up based on an improved dynamic method. The solubility of 5-fluorouracil (5-Fu) in ScCO2 with or without the cosolvent of ethanol is measured. The effects of the operating parameters including the pressure, the temperature, and the concentration of cosolvent on the solubility of 5-Fu in ScCO2 are investigated experimentally. The obtained solubility data are correlated by Chrastil and Mendez-Santiago and Teja models. The average absolute relative deviation (AARD) of the calculated value with the experimental ones is 3.52 % by the Chrastil model without cosolvent, and it is 14.6 % by the Mendez-Santiago and Teja model with cosolvent of ethanol. The results show that the addition of the ethanol as a cosolvent could significantly increase the solubility of 5-Fu in ScCO2. In addition, the partition coefficients K of 5-Fu between ScCO2 and poly(L-lactic acid) (PLLA) are determined experimentally and correlated by Banchero's empirical equation. The results show that the partition coefficient decreases with the increase of the pressure and increases with the increase of temperature. The calculated value of the partition coefficient K is well consonant with the experimental data, and the AARD is 14.7 %.