The main shaft of Ruihai mining company is only 35 m offshore.The strata are water-rich and weak.The topsoil section is constructed by freezing method.Due to the influence of tide and groundwater extraction from the surrounding sea water farms,skylight is easily formed on the frozen wall.The window opening position of the frozen wall is predicted by adopting the longitudinal temperature measurement technology of the freezer,and the measures of supplementing strengthened freezing holes are adopted,speeding up the crossing circle of the frozen wall.The effect is good and the process is worth promotion.