The invention relates to a production process of high-purity isoolefine (tert-olefin). The production process comprises a cracking reaction part, a washing part and a fractionating and refining part. The production process can adopt two implementation methods, namely fractionating and refining are carried out after water washing or fractionating and refining are carried out before water washing. In the production process, a low-molecular-weight ether washing separating column is added, so that light-component fractions which are separated from the top of an isoolefine refining column and contain low-molecular-weight ethers come into full contact with water in the washing separating column, accumulation of the low-molecular-weight ethers in the system can be effectively controlled and exhaust losses of isoolefine can be reduced; and meanwhile, new separating equipment is not added, thus lowering the cost and simplifying the operation.