With the development of THz imaging technique, there have been great demands for the improvement of THz imaging performances such as imaging resolution, imaging speed, image dimension, etc. To eliminate the influence of diffraction on imaging results and to improve the performance of THz imaging system, a lot of researchers have turned their attentions to THz digital holography. Firstly, some fundamental theories for THz digital holography are briefly introduced. Then a comprehensive description on the advances in the domestic and international research of THz digital holography is povided. These investigations exhibit that THz digital holography has great potentials to improve the imaging resolution and extend image dimension, etc. Moreover, THz digital holography has the capability of real time imaging. Those characterizations make THz digital holography a promising technique which has an exciting application and development prospect.