The invention discloses a method for increasing the contents of protein and amino acid in paddy rice by utilizing OsDCL3b. The method disclosed by the invention is characterized in that the expression of OsDCL3b gene in the paddy rice is suppressed by an RNA (Ribose Nucleic Acid) interference technology, the obvious increase of the contents of protein and total amino acids and the content of necessary amino acids such as lysine and the like in the paddy rice is firstly discovered. According to the method disclosed by the invention, the content of the protein in the paddy rice can be increased by 13.9%, the content of the total amino acids is increased by 8.6%, the content of first limiting amino acid-lysine in the protein of the paddy rice can be increased by 11.9%, the contents of another seven necessary amino acids in a human body also can be obviously increased, so that a new molecule-improving path is provided for cultivating high-protein functional and nutrient paddy rice.