It is revealed by difference spectra that cibacron blue F3GA could bind specifically to Trichosanthin(TCS). The spectral absorption maximum is on 690nm with molar absorption coefficient of 2.6×10^-3 (mol/L)^-1·cm^-1. The dissociation constant is 1.8 μmol/L, and 0.5 mol/L NaCl could dissociate the complex. Based on these results, TCS is purified from the root tuber of Trichosanthes Kirilowii by Blue Sepharose CL-6B. This method is rapid, simple, efficient and could be applied in mass preparation of TCS.