Underwater connector is an important part of the seafloor observation. Currently， the oil-filled sealing structure is complicated and it’s hard to design in project. To solve this problem， contrast the connection mode of the land-based fiber network，we presented a novel design for the contact fiber-coupled based on underwater wet-mateable the fiber connector. First， based on the analysis of Beer-Lambert law， water absorption properties and surface tension of liquid theory， we identified the ability to form the water film thickness within 5 μm at the optical fiber end faces. This thin layer water exhibit negligible absorption of the 1 310/1 550 nm because of the absorption loss can be kept within the predefined target range. The study was conducted that the loss analyses is summarized by using optic fiber in air， water， and oil based on 1 550 nm. Finally， we designed the novel optical structure based on this idea and analyzed their transmission performance. The results showed that the summary of the transmission loss is 0.17 dB and the loss measurement in the new fiber connector is 0.23 dB. The findings show that the design of the contact fiber-coupled of underwater wet-mateable is meeting the low loss requirements. Therefor， we can directly implement in-situ wet-mate interconnects in the water rather than the silicone oil based on the surface cleaning. This paper provides a new design for the optical lines in underwater wet-mate connector. This idea is expected to break the Intellectual property that built upon the work of the sealing technique of the oil-filled.