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 extraction, and the polymer solution's viscosity can reach the level of the comb-shaped salt-resistant polymer solution applied in class I oil reservoir, so it can promote the economic benefits of tertiary oil extraction from class II oil reservoir and expand the application scope.