In the recent decade, the most useful drug for the therapy of colon cancer is 5-Fluorouracil(5-FU). It has been reported to have considerable toxicity administered by intravenous injections or via alimentary treat. Though many materials have developed for drug carrier of 5-FU, there was no clinically acceptable carrier for 5-FU till now. Montmorillonite, one of clay minerals, consists of hydrated aluminum silicates that are fined grained and usually have a large space between the layers. Isomorphous substitution of cations is common. We try to intercalate 5-FU into interlayer of montmorillonite through ion-exchange. Montmorillonite with 5-FU intercalation is expected to achieve in-situ release for colon cancer therapy. In the study, 5-FU was dissolved in 100 ml distilled water as 5-FU solution. Purified montmorillonite powder will soak in 5-FU solution for a period of time ad different pH value and temperature. The intercalated amount of 5-FU in montmorillonite is measured by scanning differential thermal (SDT) analysis and UV analysis. The results showed that 4 g purified montmorillonite soaked in 0.6% 5-FU solution for 2 hours had an optimum condition for intercalation. The total amount of 5-FU in montmorillonite is about 9.13 wt%.