Micron tantalum powder (Ta) has broad application prospects in biomedical additive manufacturing and other manufacturing fields. The irregular tantalum powder was spheroidized by RF thermal plasma to improve its fluidity. The tantalum powder before and after plasma spheroidization was characterized, and the formation mechanism of satellite powder in the process of spheroidization was analyzed. The results show that the tantalum powder after plasma spheroidization has ideal sphericity and smooth surface, and its Hall fluidity and apparent density are increased from 13.6 s·(50 g)^-1 to 6.73 s·(50 g)^-1 and from 6.83 g·cm^-3 to 9.06 g·cm^-3, respectively. The spheroidization rate and spherical degree of tantalum powder can reach about 95.2% and 0.92, respectively. The formation of satellite powder in the spheroidization process is mainly caused by the collision of droplets, and with the increase in powder feeding rate, the collision probability of droplets increases, resulting in larger particle size of spherical particles due to the droplet condensation.