Deep Sea is the key area of marine science research and technology. The exploreto the Challenge Deep, Mariana Trench,the deepest oceans is the landmark and biggest challenge.In order to ensure the safety in deployment of the underwater vessels in the area,the significant wave featuresarestudied with the WAVEWATCH ⅢHindcast Data from NOAA (National Oceanic and Atmospheric Administration) and the remotely-sensed waves productfrom Jason II satellite provided by CNES (French government space agency) and other organizations from February 2005 to July 2015 is analyzed.The results show that the regional average SWH is 1.30 (Jun)-2.53 m (Jan)over the Mariana Trench.Theregional average peak period (Tp) is 8.0 (Jun)-9.6 s (Dec),The maximum monthly significant wave height are 3.03 m, 2.79 m, 2.58 m, 2.19 m, 1.74 m, 1.56 m, 1.68 m, 1.78 m, 1.85 m, 2.22 m, 2.37 m, 2.81 m, and the maximum appears in January (3.03 m), minimum in June (1.57 m).The seasonal variation has a great discrepancy.The maximum average SWH appears in winter, minimum average SWH is in summer. Spring and autumn are transitional period.For the appearance of the Rough waves with 4 m SWH, the frequency is 0.2% to 3.5%, which is more in winter and less in the other seasons.Following the required sea states conditionforsafety launch and recovery of “JIAOLONG” and others hadal submersible,May to Oct would be the practicaloperation period and in the rest months, a good sea condition would be much less.