The present invention discloses a method for AU-3 circuit emulation, including: converting frame data from an administrative unit AU-3 frame format into a tributary unit TU-3 frame format; mapping the frame data in the TU-3 frame format into a virtual container VC4 to obtain the frame data in a VC4 frame format; and emulating the frame data in the VC4 frame format. In embodiments of the present invention, frame data is converted from an AU-3 frame format into a TU-3 frame format, and the frame data in the TU-3 frame format is mapped into a virtual container VC4 to obtain frame data in the VC4 frame format. In this way, the frame data in the VC4 frame format is emulated, a requirement of transparently transmitting AU pointers in the present network is fulfilled, that is, the requirement of emulating and transparently transmitting the content of an entire AU is fulfilled.