Inter permeable network type polymer fluid loss agent and preparation method thereof

The invention discloses an inter permeable network type polymer fluid loss agent and a preparation method thereof, wherein the method comprises the following steps: (1) dissolving four monomers of 2-acrylamido-2-methyl propane sulfonic acid, acrylamide, N, N-methacrylamide and N-vinyl pyrrolidone into water, thus obtaining a mixed solution A; (2) adding natural or synthetic polymer into the mixed solution A, and introducing nitrogen (N2), thus and obtaining a mixed solution B; (3) adding an initiator and a complexing agent into the mixed solution B to react, thus obtaining a viscous product; and (4) drying and grinding the viscous product, thus obtaining the inter permeable network type polymer fluid loss agent. The method has the characteristics of large preparation amount, simple technology, low cost, high yield, moderate controllable conditions, low toxicity, low emission and the like, and the fluid loss agent is quick to dissolve and resistant to high temperature, resists salt to saturate, and has the pro