The invention discloses a plant starch synthesized related protein IbSSI, a coded gene and application thereof. The plant starch synthesized related protein IbSSI provided by the invention is 1) or 2) or 3): 1) the protein with an amino acid sequence shown as sequence 2 of a sequence table; 2) fusion protein obtained by connecting a label to the N or/and C end of the protein shown as the sequence 2 of the sequence table; and 3) the plant starch synthesis related protein obtained by subjecting the protein shown as 1) or 2) to substitution and/or deletion and/or adding by one or more amino acid residues. Experiments prove that the plant starch synthesized related protein IbSSI and the coded gene thereof provided by the invention can increase the total content of plant starch and/or change the starch quality.