Clock synchronization plays a critical role in pseudolite systems as it determines the accuracy of time-of-arrival (TOA) ranging and range-based localization. Due to the limitations of the overall cost and power consumption, how to achieve high-accuracy time synchronization and ranging for a network of nodes by relative cheap (low stability) clocks is the main research topic that will be discussed in this chapter. The basic clock model and ranging model are introduced firstly, and then a number of representative clock synchronization algorithms to deal with the scenarios of immobile anchor nodes are presented. A step further, the solutions for the network of all nodes in motion are introduced as well. Finally, a physical clock synchronization approach which consists of clock parameter estimation and clock steering is presented.