The invention relates to a method for constructing a Mia3 gene conditional knockout mouse model by using a CRISPR (clustered regularly interspaced short palindromic repeats) / Cas9 (CRISPR associated protein 9) technology. The method comprises the following steps: 1, designing sgRNA (small guide ribonucleic acid) aiming at mouse Mia3 gene Exon2-Exon7, 2, obtaining the sgRNA by using an in-vitro transcription technology, and 3, co-injecting or co-electrically transferring a targeting vector, the sgRNA and Cas9 protein to a mouse fertilized egg. Compared with a traditional ES targeting mouse model, the Mia3 gene conditional knockout mouse model constructed for the first time has the characteristics of high efficiency, rapidness, simplicity, convenience, low cost and the like, and the expression of the gene in a specific tissue or specific time can be regulated through Cre.