Tantalum powder was prepared by RF plasma process from irregular sodium reduced tantalum powder, and spherical, pore-free powder with lower oxygen content was obtained. The effects of feeding rate, carrier gas flowing rate and pressure of reactor chamber on spheroidization efficiency and powder properties were studied. The selective laser melting process of spherical tantalum powder was also explored. The results showed that tantalum powder after plasma processing possess smooth surface , high internal density, high purity and low oxygen content, and the spheroidization ratio was almost 100%.The particle size distribution became narrow after spheroidizing. Spheroidization efficiency decreased with the increasing of feeding rate, while increased firstly and then decreased with the increasing of carrier gas flowing rate. Meanwhile, lower negative pressure in reactor chamber was more favorable to obtain powder with high spheroidization efficiency. With the increasing of spheroidization efficiency, the powder flow ability, apparent density and tap density were significantly improved. The processing parameters, the feeding rate, carrier gas flowing rate and reactor pressure were optimized at 30g/min, 5.0 slpm, and 12.0 psi, respectively. Compared to the raw materials, the spherical tantalum powder hall velocity reached 5.98s/50g, the apparent density increased from 3.503g/cm3 to 9.436g/cm3 and the tap density also improved from 5.344g/cm3 to 10.433g/cm3. It was interesting to find that the oxygen content is decreased from 0.076% to 0.0481% after the plasma process. Finally, spherical tantalum powder was proved to be compatible with selective laser melting process. The SLM parts with high dense (≥99.5%) were obtained and the tensile, the yield strength and the elongation were 693MPa, 616MPa, and 28.5%, respectively.