This study aims to determine how the marketing system of Siamese Catfish (Pangasius hypophthalmus) in the Kuala Kapuas fish market. The analysis used is (1) marketing channels using the snowball sampling method (2) marketing margins (3) Farmer’s share, and (4) market structure using analysis (a) price transmission elasticity and (b) market integration. The analysis shows that (1) Siamese catfish marketing channels consist of 3 marketing channels, (2) Total marketing margin on marketing channel 1 is Rp. 2,700, -, marketing channel 2 is Rp. 6,700, and channel 3 is Rp. 8,973 (3) The share of prices received by producers in channel 1 is 73.20%, in marketing channel 2 is 87.14%, and in marketing channel 3 is 67.10% and (4) analysis of market structure is known that ( a) the analysis result of price transmission elasticity (?) in marketing channel 1 and marketing channel 2 is 0.130 and marketing channel 3 is 0.169, which means the price change is less elastic. (b) the results of market integration analysis obtained the regression coefficient ( ) of 0.1134 which indicates that the market structure is oligopsonistic