Abstract: Serine hydroxy methyltransferases（SHMTs） played an important role in the one-carbon（C1）metabolism pathway in plant cells.We identified 9 SHMT genes from the genome of Populus trichocarpa.Populus eFP resource showed that 7 PtrSHMTs were expressed in multiple tissues,among which PtrSHMT9 was the most highly expressed gene in xylem.By analysis of RT-PCR and Aspwood,PtrSHMT9 had a high level in secondary wall thickening of stem wood tissue,suggested its involvement in poplar wood formation.Using Cas9/gRNA technique,PtrSHMT9-edited mutants were prepared and 4 different knockouts were obtained.Our results provided basic information and genetic material for exploring the function of SHMT and PtrSHMT9 in trees.