Asynchronous Transfer Mode (ATM) is an emerging standard for broadband networks, packetized video is likely to be one of the most significant high-bandwidth users of such networks. The transmission of variable bit-rate (VBR) video offers the potential promise of constant video quality but is generally accompanied by packet loss, delay and delay jitter which significantly diminishes this potential, so it is necessary to provide requested QoS. In this paper, two new dynamic bandwidth allocation algorithms for MPEG videos over ATM are proposed, one is dynamic measure algorithm, another is dynamic virtual buffer algorithm, in which the authors dynamic adjust the bandwidth of MPEG video sources with a specified allowed cell loss ratios to provide QoS guarantees in an ATM network.