In order to control the sanitation of seafood in the restaurant industry and avoid incident of poisoning, different detecting methods of the hazardous substance in seafood-formaldehyde, sulfites and hydrogen peroxide were studied. In this paper, both chemical quantitative methods and rapid qualitative methods were used to study on the veracity, the limit of detection, the speed, the complicacy, the cost and the preservation of reagents, then relative ideal methods were chosen. The method of test paper is especially fitted to spot detection. The limit of detection of formaldehyde, sulfites and hydrogen peroxide are 50?g/ml, 50?g/ml and 10?g/ml, respectively. Phloroglucinol method, sulfurous acid fuchsine method and FeCl3-Phenyihydrazine hydrochloride method are also recommended for the detection of formaldehyde, with a limit of detection of 10?g/ml, 1?g/ml and 10?g/ml, respectively. However, these methods are not suitable for spot detection since liquid reagent used in these methods is not portable and hard to preserve.