Objective To observe possible mechanism of Changyi Jian in the treatment of colorectal cancer as an adjuvant therapy. Methods Eighty cases of patients with colorectal cancer during chemotherapy were randomly divided into the treating group and the control group

with 40 cases in each. The control group was only given chemotherapy

fourteen days was one circle

for two circles totally; The treating group was given Chinese medicine decoction Changyi Jian while accepting chemotherapy

one dose per day

for 28 days in total. Variation of serum levels of matrix metalloproteinases-2（ MMP2）

matrix metalloproteinases-9（ MMP9） and vascular endothelial growth factor（ VEGF） of patients in two groups were observed before and after treatment. Results There were no statistically significant differences in serum levels of MMP2

MMP9 and VEGF between the two groups before treatment（ P >0. 05）. Serum levels of MMP2

MMP9 and VEGF in the treatment group after treatment all remarkably decreased compared with that before treatment（ P < 0. 05）. There were no statistically significant differences in all indexes in the control group between before and after treatment（ P > 0. 05）. MMP2 level in the treatment group after treatment was remarkably lower than that in the control group when comparing two groups after treatment（ P < 0. 05）. Conclusion Changyi Jian could inhibit serum level of MMP2 in patients with colorectal cancer during chemotherapy

which may be one of its function mechanism of treating colorectal cancer as an adjuvant therapy.