To set appropriate threshold value(ssthresh) of slow start and eliminate network oscillation caused by bursty traffic,a new measurement-based and phase-divided slow start mechanism was proposed,which was called MP-Start.MP-Start employs effective online bandwidth measurement technology to update the ssthresh with appropriate value dynamically,and adjusts the increment of congestion window(cwnd) in different phase of the startup.MP-Start increases cwnd with half of the difference between ssthesh and cwnd,iterates and gradually closes up ssthresh,of which the increment is small at start phase and end phase and comparatively large at the middle phase of the startup of a connection,the largest increment is no more than one quarter of ssthresh.In order to improve the performance of this algorithm,a flexible parameterized model and an adaptive parameter setting solution are designed.And series simulation experiments indicate that MP-Start significantly decreases dropped packets,data transforming time,packet queue length of shared link,and also improves network performance and smoothness of connections.