The invention provides a protein for promoting the synthesis of cotton fiber green pigments as well as a gene, coding sequence and application of the protein, belonging to the technical fields of geneengineering and genetic engineering. The amino acid sequence of the protein provided by the invention is represented by SEQ ID No.1. By transfecting cotton through the coding gene or the coding sequence, the synthesizing level of fiber green pigments of the transfected cottons can be remarkably increased, and meanwhile, the non-target character introgression caused by virtue of a conventional hybridization measure can be avoided.