The invention discloses a recombinant vector for the knock-in of a human Huntington gene, a construction method of the recombinant vector and application of the recombinant vector in the constructionof a model pig. According to the recombinant vector, a human mutated Huntington exon gene is knocked in a fixed point manner for the first time, a virulence gene is knocked in by virtue of a CRISPR / Cas9 technique for the first time, and a donor vector is optimized by optimizing sfRNA, so that the probability that the gene is knocked into a positive cloned cell is increased; and by combining with apig cell nucleus transplantation technique, the probability that a directly obtained positive cell is knocked into the pig is increased, and a small human Huntington gene knock-in pig is obtained, thereby proving the efficient feasibility of the method for constructing gene modified pigs. The constructed Huntington gene knock-in model pig has behavioral characteristics such as respiratory disturbance and dyskinesia similar to human Huntington diseases, and stable heritable passage can be realized, so that a reliable model is provided for the research of the human Huntington diseases; and thenumber can be guaranteed so as to realize drug screening, gene treatment, stem cell treatment and the like, and the model can be a good human disease model.