The conventional angle adaptive control methods are not accurately combined with the actual operation data of synchronous motor, which leads to the lack of accuracy in the actual control. Therefore, a high-precision angle adaptive control method of synchronous motor based on association rules and PLC is proposed. The gain efficiency of synchronous motor is calculated, and the results are weighted to get the calculation method of ideal transmission ratio of synchronous motor angle. An association database is established to optimize the angle control gain coefficient based on association rules. The end condition of the algorithm is judged by the adaptability coefficient, the adaptive model structure is established, the angular centroid deviation distance of synchronous motor is obtained, and the angular fuzzy adaptive algorithm is designed. In the comparative experiment, the mean value of adaptability coefficient in the experimental group is 0.48/0.92 mm, and the mean values of the three control groups are 0.27/0.82, 0.42/0.57 and 0.26/0.86 mm, respectively. The experimental data shows that, compared with the conventional algorithm, the high-precision angle adaptive control method of synchronous motor based on association rules and PLC is more suitable for the actual operation of synchronous motor, and has higher precision control effect.