With hardware and software in mobile devices getting more and more powerful, it is now in the spotlight worldwide to study how to combine Augmented Reality(AR) technology with mobile devices.Three-dimensional tracking registration technique is one of the keys in mobile AR.This paper firstly outlines three methods of tracking registration in mobile AR:sensor-based method, machine vision-based method, and hybrid tracking registration, then makes detailed discussion on and inter-comparison between these methods in terms of their characteristics, finally provides summary and outlook for tracking registration technique in mobile AR.