Air entraining retaining type water reducing agent based on special molecular weight distribution and preparation method of air entraining retaining type water reducing agent

The invention discloses an air entraining retaining type water reducing agent based on special molecular weight distribution and a preparation method thereof. The water reducing agent is prepared from an isopentenol polyoxyethylene ether monomer, isoester, an unsaturated carboxylic acid monomer, a reducing agent, a chain transfer agent and an initiator through a free radical polymerization reaction. The preparation method comprises the following steps: firstly, adding a polyoxyethylene ether monomer and water into a reaction kettle, heating to 60-70 DEG C, stirring to obtain a monomer solution, adding half of an initiator, reacting for 1-2 hours at a constant temperature, dropwise adding a solution A prepared by mixing unsaturated carboxylic acid, isoester and water and a solution B prepared by mixing a reducing agent, a chain transfer agent and water at a constant speed, and reacting for 1-2 hours at a constant temperature; and uniformly adding the residual initiator in 3-5 times in the dropwise adding proce