Porous Ti-Al intermetallics materials were prepared form titanium and aluminum powders by pressureless sintering route, and the macro-morphology, phase composition, porosity, microstructure and formation mechanism of porous Ti-Al intermetallics were investigated. The results show that the volume expansion of the Ti-Al compacts is observed in all samples. The porosities of Ti-Al intermetallics are within the range of 49.88%~57.53%, and the open porosities are within the range of 47.60%~56.15%. The porous materials are made of interconnected skeleton, big pores among skeleton and small pores in the interior of skeleton. The interstitial pores in green powder compacts are the most important source of big pores of porous Ti-Al intermetallics, and the in-situ pores from the melting and flowing of aluminum powders is also significant to the formation of big pores. Small pores are from the precipitation of Ti-Al intermetallics particles in pressureless reactive sintering, and TiAl3 is the main phase of porous materials, and porous Ti-Al intermetallics are formed by thermal explosion mechanism.