Dioctyl phosphinic acid was known as an effective additive for aviation kerosene or as an extractant for some rare earths and actinium series elements. In the present paper, the addition reaction of octene-1 with hypophosphoric acid was studied. The influence of the polarity of solvents, the content of hypophosphoric acid, the purity of octene-1 and the quantities of the catalyst on the reaction has been investigated. A synthetic route which is suitable for large scale preparation has been found out. It wil...