In order to improve the heat resistance and salt tolerance of chemical wellbore plug based on biopolymer，plug that was prepared from phenolic resin crosslinker SG-3 and scleroglucan in saturated NaCl solution was studied. The effects of crosslinking temperature，time，concentration of both crosslinker and scleroglucan on the mechanical properties of plug and influence mechanism were investigated，and its ageing resistance in saturated NaCl solution at 120℃ was then examined. The results showed that the crosslinking temperature and scleroglucan concentration exerted great influence on plug’s performance. The mechanical performance of plug increased with the rising of scleroglucan concentration. Plug prepared from 3.0% scleroglucan and 1.0% crosslinker at 80°C showed both good toughness and mechanical property. And，its shape could keep stable for 40 h in saturated NaCl solution at 120°C. However，it nearly completely degraded after 72 h. Chemical wellbore plug prepared from scleroglucan and phenolic resin crosslinker displayed good heat resistance and salt tolerance. Moreover，it could gradually degrade in simulated formation water. Therefore，the plug might find applications in well cementation，completion and workover in oilfield.