Abstract: OBJECTIVE To analyze the relationships between the single drugs or the couplet medicines of the antitumor formula in Dictionary of Chinese Formula by using the association rules. MOTHODS 587 antitumor formula were collected and the relationship between single drugs and couplet medicines were analyzed by the frequent pattern and Apriori arithmetic. RESULTS Most of the drugs in antitumor formula have the functions of promoting blood circulation by removing blood stasis or promoting qi circulation and relieving pain， like Sanleng(Rhizoma Sparganii)， Ezhu(Rhizoma Curcumae)， Muxiang(Radix Aucklandiae)， Chenpi(Pericarpium Citri Reticulatae). CONCLUSION The drugs in the antitumor formula are combined used and mainly have the function of promoting blood circulation by removing blood stasis and promoting qi circulation and relieving pain. In base of this， tonifying qi and strengthening spleen， warming yang and resolving phlegm and masses drugs are also used.