The invention discloses a method for improving rice yield and a protein used thereof. The invention provides a method for cultivating the target rice, comprising the following steps of inhibiting the activity of RAY1 protein in original rice to obtain target rice; compared with the original rice, the target rice shows higher yield and/or larger grain size and/or stronger resistance to rice blast and/or higher plant height and/or longer stem internode length; the RAY1 protein is a protein composed of an amino acid sequence shown as SEQ ID No. 1 in a sequence list. The invention uses CRISPR/Cas9 technology to realize site-directed editing rice RAY1 gene, through knocking out rice RAY1 gene by frameshift mutation, the protein RAY1 is inactivated, and a new generation of rice germplasm with significantly improved yield is obtained.