Abstract: The efficient synthesis of two labeled standards trichlorfon-methoxyl-D₆ and dichlorophos- methoxyl-D₆ with CD₃OD as the precursor were presented. Esterification of phosphorus trichloride with CD₃OD provided dimethyl phosphate-methoxyl-D₆, which was used to condense with trichloroaldehyde to give trichlorfon-methoxyl-D₆. Ttrichlorfon-methoxyl-D₆ was further converted to dichlorophos-methoxyl-D₆ by alkaline hydrolysis and rearrangement. The yields of trichlorfon-methoxyl-D₆ and Dichlorophos-methoxyl-D₆ were 57.7 % and 47.3% respectively based on CD₃OD consumed. Both products were characterized by HPLC, MS, and NMR to be target compounds. Their chemical purities and isotopic enrichment were higher than 98.0%. The above compounds could be used as internal standards in the food safety field.