The cutlassfishes (Trichirus spp.) is commercial fishery targeted demersalspecies which lives in the surrounding waters of Taiwan. This study focuses on the acoustic survey in the northern waters off Taiwan, and the species composition, reproductive biology of cutlassfishes in waters off Taiwan. The mean Sv (volume backscattering strength, dB) distribution of acoustic survey showed the biological resources was concentrated in the Offshore of Fugui Cape to the Bitou Cape, and the waters of Guishan Island. From Nov. 2019 to Oct. 2021, totally 5,551 Trichiurus japonicas, 857 Trichiurus nanhaiensis and 45 Trichiurus lepturus were caught per month sampling. The sex ratio (female/total) of Trichiuru s japonicas was 64.5 % belong to 3,548 female and 1,949 male. The reproductive period was January to May and September to November estimated by the GSI and the proportion of gonad maturity. The Pre-Anal length (PAL) at 50% sexually maturity for female and male were 268.2 mm and 266.2 mm, respectively.