The invention discloses a construction method of an HDAC5 
gene knockout BHK-21 
cell line, which comprises the following steps: carrying out 
gene knockout on HDAC5 in a 
cell line BHK-21 for foot-and-mouth 
disease vaccine production by utilizing a 
CRISPR / Cas9 technology, transfecting BHK-21 cells by utilizing 
CRISPR plasmids for knocking out the HDAC5, and separating the cells to obtain a plurality of 
cell clones by utilizing antibiotic screening in combination with gradient 
dilution and a 
cloning ring method; extracting the 
genome DNA, performing PCR amplification and sequencing and successfully identifying the cell 
cloning of which one HDAC5 
gene is subjected to homozygous 
frameshift mutation, wherein the HDAC5-KO-A2 has deletion of 13 basic groups at a Cas9 predetermined 
cutting position. In the HDAC5 knockout BHK-21 cell line, the replication rate of foot-and-mouth 
disease virus is obviously accelerated, the final 
virus titer is obviously improved, and the HDAC5 knockout has no obvious influence on the 
cell growth rate, so that the HDAC5 knockout BHK-21 cell line has the prospect of being used for foot-and-mouth 
disease vaccine production. Therefore, the foundation is laid for further knocking out HDAC5 from 
suspension culture type BHK-21 cells and directly applying HDAC5 to production of foot-and-mouth disease vaccines.