The invention discloses application of a panicum virgatum L. S-adenosylmethionine synthase gene SAMS1 to change of the lignin content and further improvement on the saccharification efficiency, and belongs to the technical field of plant genetic engineering. The application comprises the following main contents: performing cloning and sequence determination on the panicum virgatum L. SAMS1 gene; constructing an interference expression vector (pANIC8B-PvSAMS1-RNAi) of the PvSAMS1 gene; transforming a panicum virgatum L. callus by an agrobacterium mediated method, and transforming an interference fragment of a target gene into lowland-type Alamo wild-type panicum virgatum L. to obtain a transgenic plant with reduced total lignin content. The expression quantity of the PvSAMS1 in the obtainedtransgenic plant is significantly reduced, the lignin content is significantly reduced, and the saccharification efficiency is significantly improved. Through regulation and control of lignin metabolism by the identified panicum virgatum L. SAMS1, a novel target can be provided for molecular breeding in future.