The invention relates to an alternating current detection circuit, in particular to an alternating current detection circuit based on a bidirectional optocoupler. According to the technical scheme, the alternating current detection circuit based on the bidirectional optocoupler comprises a transient suppression diode. The transient suppression diode is connected with a first input end of a bidirectional optocoupler primary circuit through a first resistor. A first end of a bidirectional optocoupler secondary circuit is connected with VCC (volt current condenser). A second end of the bidirectional optocoupler secondary circuit is grounded through a second resistor. Second capacitors are connected to two ends of the second resistor in parallel. By the use of the transient suppression diode, low noise interference in the circuit can be eliminated, and transient high voltage in the circuit can also be suppressed. By the use of the bidirectional optocoupler in the circuit, positive-direction alternating current signals and negative-direction alternating current signals can be detected, high voltage and low voltage are effective isolated, and subsequent circuit systems are protected.