Abstract: In order to enhance the toughness of mining polymer foam, polyethylene glycol (PEG), an organic material, was added to modify the toughening effect of foam. The effect of PEG modification with different molecular weight was studied by scanning electron microscope, thermogravimetric test, oxygen index test, cone calorimetric test, compressive strength test, foaming and curing time test. The results show that: PEG with different molecular weight can effectively increase the compressive strength of phenolic resin foam and reduce its pulverization rate. When the molecular weight of PEG is 1 000, the addition of 6% has the best toughening effect, the compressive strength reaches 0.155 MPa, and the pulverization rate decreases to 1.3%. Adding a certain amount of PEG can effectively increase the foaming ratio of phenolic resin, but at the same time, it will increase the shrinkage and curing time of its foam. The pore structure of PEG modified phenolic resin foam is more uniform, and the pore size of foam is also more uniform, mainly because the PEG that does not react with the phenolic resin plays the role of surfactant, and can better mix the curing agent with the resin. Compared with the thermal stability of phenolic resin foam with different PEG molecular weight, the larger the molecular weight, the worse the thermal stability of phenolic resin foam with more PEG molecular weight.