Owning to the progression of science and technology, increasing techniques for in vivo cell tracking have been applied in medical research; they include radionuclide imaging, magnetic resonance imaging, optical imaging, etc. These imaging methods have their own characteristics in specificity, sensitivity and manipulation mode. Researchers should choose the appropriate method while taking the following into consideration: requirement of the image, object of the image, the aim of the image, and the characteristics of each imaging method. In this paper we summarize the techniques of cell tracking in vivo.