The invention discloses a preparation method of long carbon chain nylon 1211. The preparation method comprises the following steps: using dodecamethylenc diamine and undecanedioic acid as main raw materials, carrying out a preparation technology for synthesizing nylon 1211 salt in an alcohol solvent, adding a catalyst and an antioxidant into the nylon salt after drying, carrying out temperature rise and pressure rise, and carrying out a polymerization reaction to obtain a nylon 1211 synthetic process. The product is superior to nylon 11 in the aspect of structure performance, and has good mechanical and thermodynamic properties; according to the method, the product is prepared through high pressure, the molding cycle is effectively shortened, the production efficiency is improved, the requirements of people on automobile industry, space and aircraft industries and electronic and electrical industries can be met, and the product has good market prospect.