In this paper, a typical Li- and Ta/Sb-modified alkaline niobate-based ceramics prepared by conventional sintering and two-step sintering were investigated in terms of their phase transition behaviors and various properties. The phase structures of the ceramics sintered by conventional sintering shifted remarkably from a polymorphic phase transition (PPT) to a tetragonal symmetry with the increase of sintering temperature. However, the ceramics sintered by two-step sintering maintained PPT over a wide sintering temperature range. Similar to that, the various properties of the ceramics sintered by conventional sintering are strongly dependent on sintering temperature and the ceramics with good properties can only be obtained in a narrow sintering temperature range, while the ceramics with excellent properties were obtained by two-step sintering over a wide sintering temperature range. The results indicate that two-step sintering is an effective way to broaden the sintering temperature range of (K, Na)NbO(3)-based ceramics.