Abstract: The present disclosure belongs to the technical field of plant genetic engineering, and discloses a gene for controlling the rice grain number per panicle and its use. Nucleotide sequence of OsCKX11 is SEQ ID NO. 1, nucleotide sequence for coding protein region is SEQ ID NO. 2, amino acid sequence of the encoded protein is SEQ ID NO. 3. The disclosure constructs an OsCKX11-knocked-out vector using CRISPR/Cas9, and identifies multiple independent homozygous lines through PCR amplification and sequencing methods, and provides a mutant in which specific knockout of gene OsCKX11 of the rice leads to an increase in cytokinin levels and an increase in grain number per panicle. Based on the biological function of OsCKX11 to increase the rice grain number per panicle, methods such as gene editing, natural allele replacement, RNA interference, or molecular assisted breeding can be used to improve existing rice varieties.