The rule of morphology evolution of products in producing tantalum by FFC was studied. Results show that overhead oxide changes into off-grade oxide of tantalum during electrolysis. The off-grade oxide of tantalum is not stable, so it combines metal ion to interphase of tantalite. When the content of oxygen in the interphase decreases to a certain level, the interphase will resolve to produce particles of 200~400 nm, which form cellular polymer by single stranded. The electrical property of tantalum powder with different electrolysis time was analyzed. The longer the time is, the bigger the capacity is.