Abstract: IPDV is an important performance metric of IP network which reflects network path’s workload characteristics. Based on a path queueing model, it is found that the reflection IPDV has on path workload is influenced by the interval of probes’ sending time; the IPDV measured by the existing method just reflects path workload superficially for inappropriately selected reference delay and the limitations of the sampling method. The packet-pair sampling measurement method proposed can improve the reflection capability by selecting the proper reference delay and avoiding the limitations of the sampling method; What is also determined is the minimum interval between the two packets in a packet pair. Experiments on an Internet path validate the improved reflection capability of the packet-pair sampling method and the interval time’s influence on it.