Abstract: A pilot plant of Type 2-7 stainless steel cascade enriching highly concentrated ~(13)C using CO_2-di-n-butylamine-triethylamine chemical exchange system was set up; The mathematical model of the multistage trapezoid cascade was established, which describes the function relation among separation factor a, concentration of raw material x_i, flow of each column L, diameter of column D, height of column H, equivalent diameter ofpacking D_e, productive rate of cascade P and concentration of products x_p The cascade was run, and the concentrative rate of the cascade was sped up and the separative capacity of the cascade was fully developed. The concentrationof ~(13)CO_2-products remained more than 93 atom % and up to 99.288 atom % during 150 days of drawing-off of products at 100g ~(13)C/a.