Accurate measurement of network bandwidth is crucial for many Internet applications and protocols.Based on the analysis of IGI algorithm used to measure network available bandwidth

an improved measurement algorithm has been proposed.The experiment results show that the improved algorithm outperforms the current IGI in the evaluation precision and tracing capability.On the other hand

an improved PTR algorithms has been introduced to make the measurement value more stable and more accurate

especially when the bottleneck link on the network path is under high utilization

without making the measurement time added too much and bringing two much network overload into the measured network path.