Abstract: Aiming at the problem of water mist condensation on the fiber end face in a high-power fiber laser system, the most important factor causing this problem is that the traditional optical fiber connector does not have the moisture-proof sealing performance. The connector structure assembly and use process are analyzed in-depth, and the causes of the moisture-proof seal defects are pointed out. Through technological innovation and process improvement, a moisture-proof seal fiber connector is designed and completed. The principle and structure of the moisture-proof seal of the new connector are introduced. The main performances of the new connector are tested comprehensively, including immersion test, constant damp heat test, online application test. The experimental results show that the new connector has a better moisture-proof seal with IL less than 0.2 dB.