The embodiment of the invention discloses an IP address alias analyzing method and device. The IP address alias analyzing method and device is used for improving the precision of alias analysis. The method comprises measuring a first IP address path between a source node and a target node; obtaining the first IP address of every node inside the first IP address path; dividing the first IP address into a plurality of subnets to compose a subnet set; selecting a second IP address and a third IP address of the first subnet of the subnet set; obtaining a second IP address path containing the second IP address and a fourth IP address, and a third IP address path containing the third IP address and a fifth IP address from the first IP address path; when determining that preset conditions are met, marking the second IP address and the fifth IP address as a first router and the third IP address and the fourth IP address as a second router. The embodiment of the invention also provides the IP address alias analyzing device. The IP address alias analyzing method and device can improve the precision of IP address alias analysis.