Using conventional solid-phase sintering technique combined with a special atmosphere controlling technique, KNN-based lead-free transparent ceramics, xBa(Sc0.5Nb0.5)O3-(1-x) (K0.5N0.5)NbO3 (xBSN-(1-x) KNN), are prepared and investigated. Their microstructure, dielectric performance, ferroelectric performance and optical transparency are investigated. The results show that such ceramics are each with a pseudocubic-Perovskite structure, without any other impure phase. Their grain size is comparable to the light wavelength and the grains are highly condensed without evident crystal borders. For x=0.05, the d33 reaches up to 110 pC/N maximally and the 2Pr =25.4 C/cm2. Moreover, such ceramics are each with an excellent transparency. Their optical transparency reaches about 54%, In the near-infrared wavelength 2500 nm, their optical transparency is near 83%. Such ceramics are a type of environment-friendly lead-free transparent ceramics which may be promising in replacing lead-based transparent ceramics.