In this work, facile synthesis of bright CdS/CdSe/CdS@$SiO_2$ nanoparticles with 72% of quantum yields (QYs) retaining ca. 80% of the original QYs is presented. The main innovative point is the utilization of the highly luminescent CdS/CdSe/CdS seed/spherical quantum well/shell (SQW) as silica coating seeds. The significance of inorganic semiconductor shell passivation and structure design of quantum dots (QDs) for obtaining bright QD@$SiO_2$ is demonstrated by applying silica encapsulation via reverse micro-emulsion method to three kinds of QDs with different structure: CdSe core and 2 nm CdS shell (CdSe/CdS-thin); CdSe core and 6 nm CdS shell (CdSe/CdS-thick) and CdS core, CdSe intermediate shell and 5 nm CdS outer shell (CdS/CdSe/CdS-SQW). Inevitably lower photoluminescence quantum yield (PL QY) than pristine QDs Due to formation of surface defects.However, the retaining ratio of pristine QY is different in the three silica coated samples; CdSe/CdS-thin/$SiO_2$ shows the lowest retain ratio (36%) while the retaining ratio of pristine PL QY in CdSe/CdS-thick/$SiO_2$ (84%) and SQW/$SiO_2$ (80%) appears to be. Thick outermost CdS shell isolates the excitons from the defects at surface, making PL QY relatively insensitive to silica encapsulation. The bright $SiO_2$-coated SQW sample shows robustness against harsh conditions, such as acid etching and thermal annealing. The high luminescence and long-term stability highlights the potential of using the SQW/SiO2 nanoparticles in bio-labelling or display applications.