This study aims to identify the starting point in the territory of formaldehyde contamination in Meureudu Biji Nangka Fish (Mullidae sp.). Formalin test in spec test, the sample to be used in this study is ikan biji nangka (Mullidae sp.) obtained from each of the fish sellers in the market, and the fish boat Mugee Meureudu fish. Samples were taken and put into plastic and taken to the laboratory Peternakan Meureudu. Biji nangka minced fish samples as small as possible (or blender) samples to be used as much as 10 grams, add 20 ml of hot water, then stirred and allowed to cool first, take a sample extract (water only, after being mixed with the material to be tested) of 5 ml, and add 4 drops of Reagent a, then add 4 drops of Reagent B, beat for a while and wait about 5-10 minutes, observe the color change occurs, change the color purple indicates the content of formaldehyde (formalin), the color density formed purple indicates the level of substances in the sample extract. From the results of research in the district Meureudu then there are a number of samples positive outcome of the Mugee. Key words: Mullidae sp, formaldehyde, kit test, Meureudu.