The invention relates to an organic antimony compound and a preparation method and application thereof. The structure of the organic antimony compound is shown as the formula (I), wherein R is the linear chain of C8 to C16 or an alkane group with a branched chain, a C8-C16 ester group or a C8-C16 alkylene group; and the value of n is 3 or 5. The preparation method includes the following steps that: organic acid anhydride shown as the formula (II) and aliphatic alcohol shown as the formula (III) are taken to carry out reflux reaction under the temperature of 65 DEG C to 100 DEG C for 3 to 4 hours, antimony compound is then added, reflux reaction takes place under the temperature of 100 DEG C to 130 DEG C for 1 to 2 hours, cooling and filtration are carried out after the reaction, distillation under reduced pressure is carried out until no fraction is distilled, and thereby the organic antimony compound shown as the formula (III) is obtained. The antimony compound is the halide or oxide of antimony; and the P in the formula (III) is the linear chain of C4 to C8 or an alkane group with a branched chain. The organic antimony compound applied in PVC heat stabilizer has excellent initial coloration resistance, and nearly does not have toxicity, materials are cheap, and the organic antimony compound also has excellent ultraviolet light resistance.