Satellites in Satellite IP network (SIPN) run along its orbit and have fixed periods. It is possible to estimate the encounter time between two satellites using their history encountering information. We introduce a method to estimate the time. Based on the encounter time information estimated, a new routing method, named Encounter Time Estimating Routing (ETER), is presented in the paper. ETER firstly estimates the encounter time among satellites. Secondly, it forms a graph, assign values of encounter time as the weight of edges. Then ETER path algorithm, a modified Dijkstra algorithm, finds the best routing set for packets. Finally, ETER forward each packet using ETER forwarding algorithm. The simulation result shows that ETER has better performance on packet loss rate and transferring throughput under all traffic loads; under lower traffic loads, the average end-to-end delays of ETER is a little higher than Epidemic routing, but lower than PKR; under higher traffic loads, the delays is lower than PKR and close to Epidemic routing.