Abstract: In this paper,the key techniques of safety reliability monitoring in subgrade construction in permafrost are provided according to the analysis of the interaction process between subgrade construction and the permafrost.The key techniques have the techniques,motoring methods and data analysis methods.The safety reliability of permafrost subgrade construction depends on the thermal stability of the permafrost around and at the bottom of the construction and the thickness of deformed road-base fill and the beneath thawed layer. Therefore,the soil temperatures at different depths under the railway base surface and the deformation of railway base fill during the annual freezing and thawing periods are the main indexes in the long-term reliability monitoring of road-base construction in the permafrost.The extreme bed natural conditions demand that the means of monitoring must be reliable,durable and flexible.This paper discusses one set of monitoring system It has been verified with field test.Besides,the paper presents a method for analyzing monitored data for enhancing the judgment of the permafrost construction reliability.