Braided comb-shaped thickener for salt-resistant polymer

A braided comb-shaped salt-resistant thickening agent for tertiary oil extraction from class I oil reservoir is disclosed. The agent is polymerized with monomer (A) and monomer (B), and monomer (A) is one or multiple water soluble non-saturated compound(s) with alkenyl chain, while monomer (B) is at least one compound with the following formula: Monomer (A) is preferably acrylamide, ethenyl pyrrolidone, 2-acrylamide-2 methylpropane sulfonic acid, and acrylic acid or the mixture of the above said compounds, and in the formula of monomer (B), A is COOH, OH, SO3H, R1 and R2 are H or C1-C12 alkyl, R3 and R4 represent C1-C12 alkyl, C1-C12 alkylaryl, C1-C12 alkyl ether or C1-C12 alkyl ester group. This thickening agent has fine water solubility and good property to thicken water medium. The polymer's molecules present a braided comb-shaped structure in water solution with fine salt-resistant performances. The agent can be used together with the water extracted from oil mines to compound the polymer for tertiary oil