In this study, spherical TC4 alloy powders were prepared by gas atomization. The surface and internal pore defects of TC4 alloy powders with different particle sizes were characterized by SEM, synchrotron radiation CT scanning and three-dimensional reconstruction. The experimental results show that the surface of the powder gradually changes from the condensed shrinkage trace to smooth surface with the decrease of particle size. The number and size of pores in powders also gradually decrease with decreasing the particle size. The formation of anomalous powders with the morphologies of wrapping, conjoined, ellipsoid and satellite is resulted from the difference of coagulation and spheroidization time and the different flight trajectories during the atomization process. The results of three-dimensional reconstruction by synchrotron radiation CT scanning show that the porosity and pore size of the powder increase with the increase of its particle size. The authors propose that if the metal droplet could be completely broken into tiny droplets during atomizing prior to its solidification by tailoring the atomizing parameters, internal porosity defects would be effectively minimized.