The comparative study of high temperature and high pressure (HTHP) and chemical vapor deposition (CVD) single crystal diamonds was carried out. HTHP Ⅰb, HTHP Ⅱa, and CVD (100) single crystal diamonds were investigated by HRXRD, Raman and lattice distortion detector. The results of HRXRD and Raman demonstrate that the crystal quality of HTHP Ⅱa single crystal diamond is close to that of natural diamond. The full width at half maximum of rocking curve and Raman are respectively 0.015° to 0.018° and 1.45 cm-1 to 1.85 cm-1. The optical birefringence images measured by lattice distortion detector show that there are two kinds of stress-induced birefringence distribution in HTHP Ⅱa single crystal diamond, one is not obvious, the other is symmetrically radiated along the direction of <110>, and there is no lattice distortion in other regions. The strain structures of HTHP Ⅰb and CVD (100) single crystal diamond are relatively dispersed with complex lattice distortion. Furthermore, the defects of (100) plane of three types of single crystal diamond were analyzed by plasma etching method. The results show that the dislocation density of HTHP Ⅱa diamond is the lowest among the three types, which is only 1×103 cm-2. The research work provides experiment support for selecting the substrate to prepare high-quality and large-size CVD single crystal diamond.