Transparent piezoelectric ceramic, as a lead-free multifunctional ceramic, is in dire need of development for future high-tech industries. However, excellent piezoelectricity and high transmittance are usually hard to achieve simultaneously, mainly due to the two mutual restricting factors (phase structure and grain size). In this work, we report that high piezoelectricity and transmittance can be obtained simultaneously in K0.5Na0.5NbO3 ceramics via Sr(Sc0.5Nb0.5)O-3 (SSN) modification. The superior piezoelectric performance comes from the retain of orthorhombic phase structure at room temperature (RT); while the high transparency (>70% at 780nm) can be attributed to the improved relative density and reduced grain size via SSN modification. Remarkably, in the sample with 0.05SSN modification, we realized a comprehensively high transmittance (73% at 780nm) accompanied by a superior piezoelectric constant (d(33)=101pC/N), which outperform other reported KNN-based transparent ceramics to our best knowledge. Our results may provide insight for further developing the transparent piezoelectric ceramics by controlling the grain size and phase structure.