A communication circuit for indoor and outdoor units of an air conditioner and an air conditioner. The circuit includes an outdoor unit sending module, an outdoor unit receiving module, an indoor unit receiving module, an indoor unit sending module, a weak electricity grounding end and a voltage regulation rectifying circuit, wherein the voltage regulation rectifying circuit, the outdoor unit receiving module, the outdoor unit sending module, the indoor unit receiving module, the indoor unit sending module and the weak electricity grounding end are sequentially connected in series to form a loop; the voltage regulation rectifying circuit is configured to convert alternating current of a main control board of an indoor unit into direct current, and supply electricity to the loop.