Using conventional solid-phase sintering technique combined with a special atmosphere controlling technique, KNN-based lead-free transparent ceramics, x Ba(Sc0.5Nb0.5)O3-(1-x) (K0.5N0.5)NbO3 (xBSN-(1-x) KNN in simplified form), are prepared and investigated. The XRD, micro-structure, dielectric performance and optical transparency are investigated. The results show that such ceramics are of pseudocubic-Perovskite structure without any other impure phase. The grain size is comparable to the light wavelength and the grains are highly condensed without evident crystal borders. When x=0.05, d33 can reach up to 110 pC/N maximally. Such ceramics are of excellent transparency and the optical transparency reaches about 47 % in the visible light range,and the optical transparency is near 70 % at the near-infrared wavelength 2 500 nm. Such ceramics are a type of environment-friendly lead-free transparent ceramics which is promising in replacing lead-based transparent ceramics.