Due to the great potentials of tantalite and niobate materials in ferroelectric and photocatalytic applications, development of proper tantalum or niobium precursors is urgently need. In this work, a simple novel route to synthesize environmentally friendly aqueous tantalum and niobium precursors has been developed using cheap and stable Nb2O5 or Ta2O5 as starting source. Using home-made Ta and Nb precursors, several photocatalytic nanopowders such as BiNbO4 and BiTaO4, and ferroelectric ceramics such as 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT), have been prepared by a modified PC method. These powders and ceramics from polymeric precursors have low crystalline temperature and transformation temperature with uniform grain distribution, compared to conventional solid phase reaction (SSR). Pure triclinic phase of BiNbO4 powders can be obtained at 700°C instead of 1020°C of SSR, with excellent photodegradation activity of methyl violet. PC-derived PMN-PT ceramics also exhibit better ferroelectric and piezoelectric properties. All these indicate that this is an attractive and flexible approach using environmentally friendly water-soluble tantalum and niobium precursors for fabrication of tantalate and nibonate functional materials.