The invention relates to a rosin polycondensate air-entraining agent and application thereof. The air-entraining agent is prepared in the preparation method which comprises the following steps: 1) heating to melt rosin or rosin and lignin, mixing well, and isomerizing to prepare an isomerized product A; 2) adding maleic anhydride or maleic anhydride and concentrated sulfuric acid, and polycondensating to prepare synthetic resin B; 3) adding polyethylene glycol and glycerol and/or concentrated sulfuric acid, and carrying out graft esterification to prepare an esterified product C; 4) adding a foam stabilizing component, and preserving the temperature for reaction; 5) cooling, adding alkali solution for neutralization, controlling the pH to be 8-13, preserving the temperature for reaction, and adding tap water so that the solid content reaches 30 plus or minus 1 percent, thereby completing the preparation of the rosin polycondensate air-entraining agent. The air-entraining agent provided by the invention has excellent water solubility, air-entraining property and bubble maintaining performance, and is applicable to various kinds of concrete or mortar for industrial buildings, civil buildings, highways, railways, bridges, tunnels or hydraulic engineering, in particular to special low-slump concrete doped with fly ash such as roller compacted concrete.