Abstract: Bending, noise, fluid fluctuation are the main features of pipline in ship. Aiming at these problems, this paper proposed a ship pipeline leakage detection system using linear Sagnac optical fiber interferometer. This system designed a optical fiber sensor by selecting the length of eliminated blind optical fiber to find out the optimal optical fiber position. The design process of this system was based on four key elements: eliminating blind area of zero frequency, avoiding repeating zero frequency, easy to emerging of zero frequency, and preventing noise frequency pollution. Moreover, this paper integrated circuit, optical path and detector into monitor case, and made a detection system into instrument. Experiment results show that leak signal can be precisely detected by instrument in time. This monitor instrument can effectively solve how to detect the complexity ship pipline precisely in excellent stability.