The invention discloses an organic phosphate catalyst and a preparation method thereof. The catalyst has a structural formula as shown in the specification. The preparation method comprises the following specific steps: reacting phosphorus trichloride, isoprene and tri(2-chloroethyl)phosphate so as to obtain an intermediate I, and reacting the intermediate I with ethyl magnesium bromide, thereby obtaining the organic phosphate catalyst. The catalyst is used for synthesizing carbodiimide oligomers and high polymers from isocyanates. The synthetic process of the catalyst is simple and easy to realize, mild in reaction conditions, simple in raw materials and low in production cost. The solid catalyst has high catalytic efficiency, can realize catalysis at a low temperature, and can be recycled without losing the catalytic activity.