The invention discloses a control method for optimizing a thyristor controlled transformer type controllable electric reactor. The control method comprises the following steps: 1) detecting load three-phase power, 2) calculating a current harmonic wave distortion rate, 3) judging whether harmonic waves cross the limit, 4) constructing the grading function of a power quality index, 5) utilizing the analytic hierarchy process to determine the weight of the index, and 6) determining a three-phase firing angle with the purpose of enabling the power quality to be optimum. On the condition of not increasing the number of equipment, depending on the optimizing selection of the firing angle of a controllable electric reactor thyristor, the control method lowers the harmonic waves generated by the electric reactor, and improves the power quality of a circuit.