The invention discloses a power cable sheathing compound with good thermal stability. The raw materials of the power cable sheathing compound comprises, by weight, 15-35 parts of Ethylene Propylene Diene Monomer, 5-20 parts of low density polyethylene , 20-60 parts of hydrogenated butadiene-acrylonitrie rubber, 0.2-0.8 part of 2,5-dimethyl-2,5-di(tert-butylperoxy) hexane, 1-2 parts of dicumyl peroxide, 1-2 parts of maleic anhydride, 1-2 parts of phenyl trichlorosilane, 20-30 parts of modified composite emulsion, 0.5-1.2 parts of Epoxidized linseed oil, 1-3 parts of chlorinated paraffin, 0.1-0.6 part of black factice, 0.5-1.1 part of tetramethyl orthosilicate, 15-25 parts of silk fiber, 20-40 parts of lignin, 5-15 parts of nanosilicon dioxide, 20-40 parts of white carbon black and 1-8 parts of antimonous oxide. The power cable sheathing compound has good tenacity, excellent thermal stability and good mechanical property, and can effectively avoid phenomenon of brittle failure.