Chemical constitution was thoroughly investigated to explicit active ingredients and action mode through isolation and identification of compounds using silica gel column chromatographic, MCI gel column chromatographic and preparative thin layer chromatography method with aerial part of Codonopsis pilosula (Franch.) Nannf as source material. Results obtained as follows: (1) eight compounds were isolated from aerial part of Codonopsis pilosula including two steroids, two fatty acids, one glyceride, and three glycolipids: αspinasterol (1), (22E)5α,8αepidioxyergosta6,22dien3βol (2), 9,12linoleic acid (3), 1αlinoleoylglycerol (4), stearic acid (5), 3αlinolenoylglycerol 1O ［αDgalactopyranosyl(1→6)OβDgalactopyranoside (6), 3αlinolenoylglycerol 1OβDgalactopyranoside and 3(7,10,13hexadecatrienoylglycerol) 1OβDgalactopyranoside mixture (7). (2) Compounds 2, 4, 6 and 7 were firstly isolated from C. pilosula. (3) Compounds 1，2，3，6 and complex 7 could inhibit activities of pancreatic lipase. As the pancreatic lipase was responsible for metabolism of lipid, compounds 1，2，3，6 and complex 7 probably would reduce lipid accumulation and were defined as antiobesity ingredients of C. pilosula.