Because of the characteristics of temporal constraints, there may be a relationship between structural and temporal information in temporal XML. This chapter focuses on this and studies a temporal XML index based on linear order. Firstly, it discusses linear order partition, which provides a mathematical framework to the temporal index. Secondly, it researches algorithms on linear order branches, which are crucial in creating the index. Thirdly, it studies the querying paths based on temporal XML. Finally, it implements simulations with large number of testing data whose results indicate that the index is feasible and effective.