Abstract: 1-(4-Methylbenzyl)-2-methyl-octahydro-isoquinoline hydrochloride( 1 )is the key intermediate to prepare a new type of antitussives agent phosphate dimemorfan. 4-methyl-phenylacetic acid as a raw materials, was chlorinated with thionyl chloride to obtain 4-methyl-phenylacetyl chloride, followed by reaction with 2-cyclohexenyl amine, then cyclization, reduction, methylation and salt formation by HCl were taken out to give the desired product 1 . The total yield is 54%, and the purity is greater than 98%. This synthetic process is characterized with available raw materials, simple in operation with high yield and purity, and suitable for large-scale production.