The present invention relates to a cycloalkyl-substituted N-5,6,7-hydro-quinoline-8-aryl imine nickel complex catalyst and a preparation method and application thereof. The N-5,6,7-hydro-quinoline-8-aryl imine nickel complex catalyst has a structural general formula as shown in a formula I. The catalyst complex can well catalyze vinyl polymerization under the effect of cocatalyst methylaluminoxane, diethylaluminium chloride and the like to obtain a low molecular weight high branching degree polymer, the catalyst complex also has high activity, the highest activity is up to 5.33*106g (PE) mol (Ni) <-1>h<-1>; the molecular weight of obtained polyethylene wax is 1430-3330g / mol, the molecular weight distribution is between 1.38-1.92, the branching degree is up to 422 / 1000C, and the catalyst complex has good prospects for industrial application.