With the popularity of Internet, IPv4 technology has been unable to meet the requirements of this rapid development; the corresponding router technology also needs to be improved. In order to be more adaptive to the development of global integration process and promote Internet technology's widespread and applications in worldwide, the performance of the routing algorithm used in routers must be improved. In traditional QoS routing algorithms all use the existing network layer's QoS parameters as the characteristic parameters of its routing calculations except delay and jitter, so it can not fully reflect the quality of service. Now we present a kind of QoS routing algorithm based on risk analysis which is suitable for IPv6, we can get a max number of calls according to network resources, thereby reducing the time of call admission control.