Abstract: Three series of 36 quaternary ammonium salts containing hydrogenated nopyl were synthesized using β-pinene as the starting material. Their inhibitory rates on pathogenic fungi of Sphaeropsis sapinea were tested. The inhibitory mechanism of four compounds including bis(hydrogenated nopyldimethylammonium bromide)(14), hexamethylene-1, 6-bis(hydrogenated nopyldimethylammonium chloride)(26), tetramethylene-1, 4-bis(hydrogenated nopyldiethylammonium bromide)(28) and 1, 4-dibenzyl-bis(hydrogenated nopyldimethylammonium bromide)(31) on pathogenic fungi of S. sapinea were preliminarily explored from three aspects of mycelial dry weight, cell membrane permeability and mycelial structure. The results showed that most of the quaternary ammonium salt compounds containing hydrogenated nopyl had good inhibitory effect on S. sapinea, and the inhibitory effect of gemini quaternary ammonium salts containing hydrogenated nopyl on S. sapinea were stronger than that of single quaternary ammonium salts. The inhibitory rates of most quaternary ammonium salt compounds containing hydrogenated nopyl were more than 90% or even 100%, at a mass concentration of 50 mg/L, which were much higher than those of commonly used fungicides chlorothalonil and carbendazim. The preliminary antibacterial mechanism study showed that the dry weight of mycelium decreased, the relative conductivity increased significantly, and the morphology and structure of mycelium changed significantly when they were treated by above-mentioned four compounds. Based on these phenomena, we speculated that quaternary ammonium compounds could inhibit the mycelial growth of S. sapinea by damaging the integrity of cell membrane and changing the morphology and structure of mycelium.