The present disclosure discloses a method, apparatus and system for transmitting multimedia data. After accessing to a multimedia conference room, a client encodes multimedia data to be transmitted, and transmits the encoded multimedia data to a multi-point control unit. The client receives a multimedia data packet sent by the multi-point control unit. The multimedia data packet is obtained by the multi-point control unit via encapsulating multimedia data sent by at least one client in the multimedia conference room. The client decodes the multimedia data packet, composes multimedia data obtained after decoding the multimedia data packet, and displays the composed multimedia data.