The invention provides a low-volatility unsaturated polyester primer which consists of a main agent, a solvent, an accelerant and an initiator, wherein the main agent comprises the following components in parts by weight: 30-60 parts of unsaturated polyester resin, 20-40 parts of filler, 0-10 parts of pigment, 3-5 parts of polishing agent, 3-5 parts of styrene, 0.1-0.2 part of antifoaming agent, 0.3-0.5 part of solvent volatilization inhibitor, 0.1-0.2 part of leveling agent and 0.2-0.6 part of anti-settling agent. The primer is characterized by being prepared from vacuumized allyl ether unsaturated polyester resin, wherein the resin has the characteristic of generating a quick crosslinking reaction with the adopted active solvent (styrene); by adding the solvent volatilization inhibitor, the volatilization of the solvent can be effectively reduced; and moreover, the proportion of the construction effective solid components reaches 100%, the volatilization of the solvent is reduced by the solvent volatilization inhibitor, and thus the aims of low volatility and environmental protection are achieved.