Establishing rapid and correct detection methods to identify cod fish species is very important to promote labels correction and control fraud behavior. This study developed a systematic method mainly using visible loop-mediated isothermal amplification (LAMP) to identify cod and oil fish that are commonly found from the Chinese market. Specific primer sets were designed based on the Cytb gene of each species, and four primer sets were found to successfully achieve very high specificity in identifying the corresponding targeting species, including Gadus morhua, Gadus macrocephalus, Theragra chalcogramma and two oilfish species (Ruvettus pretiosus and Lepidocybium flavobrunneum), respectively. The discrimination of Merluccius australis, Dissostichus eleginoides and Anoplopoma fimbria can be realized by a two-step method with only LAMP or qPCR. The relatively systematic primers and methods explored in this study can be successfully applied against the serious mislabels and adulterations in cod fish market.