The invention discloses a circulating-current-free control method for a AC-AC frequency converter; Aiming at the possible occurrence of current demand signal jitter when the current passes zero, in the method, a dead area is added to the current demand signal, and no switching process is conducted when the current set signal is in the dead area; a switching command is sent out only when the current demand signal enters the dead area in one direction and leaves the dead area in another direction; when the current demand signal stays long in the dead area over 10ms, the switching command is given directly, so that the actual current voltage always stays in an AC state. If all the thyristors of in-phase in the positive and negative groups stay in an off state over 5ms, a preset threshold, an on signal is forcibly sent to the thyristors in the positive or negative group to ensure that the three-phase thyristors can be matched correctly, so as to output the three-phase alternating current needed by a motor.