Trihydroxymethylaminomethane (TAM) is a new crystal analyzer with both chemical stability and X-ray analytical performance better than pentaerythrite(PET). The X-ray topographic experiment results show that there are not only a variety of dislocations with Burgers vectors b=±[100], ±[010], ±[001], ±[101], ±[101] and ± [011] etc, but also macroscopic inclusion arrays or isolate inclusions. The planar defect parallel to (001) plane is occured rarely. Origins of defective formation are discussed briefly.