The invention discloses a phosphite/N-heterocyclic carbene-containing mixed nickel (II) complex, and a preparation method and application thereof. The chemical formula of the mixed nickel (II) complex is Ni[P(OR1)3][(R2NCH2CH2NR2)C]X2. The phosphite/N-heterocyclic carbene-containing mixed nickel (II) complex can efficiently catalyze cross coupling reaction between chlorohydrocarbon and neopentyl glycol biborate in the presence of potassium methoxide to prepare the neopentyl glycol arylborate, which is an example of the cross coupling reaction catalyzed by the mixed nickel (II) complex by using phosphite and N-heterocyclic carbene as auxiliary ligands.