Owing to their good osseointegration property, calcium silicate (CS) bioceramics have been extensively studied in recent years. Nevertheless, the excessively high environmental pH value of CS bioceramics will limit their clinical application. The purpose of this work is to reduce the dissolution of Ca and Si ions from the pure CS bioceramics by modifying its surface structure and chemical composition with Zn2SiO4 nanoparticles (Zn–CS bioceramic). The results indicated that the dissolution of Ca and Si ions from the CS substrate obviously decreased by the surface modification, and the pH value of the soaking liquid was also effectively controlled. SEM observation and EDS analysis showed that apatite mainly formed on the wall of the internal pores under the Zn-containing porous surface layer when the Zn–CS bioceramic was soaked in the simulated body fluids (SBF). Moreover, cell adhesion assay proved that mouse osteoblast cells (MC3T3) well adhered and spread on the Zn-containing porous surface layer, and the apatite formed on the surface of the Zn-containing porous layer during the incubation process. Better bioactivity and the osseointegration property can be expected for Zn–CS bioceramic. The surface modification with Zn2SiO4 nanoparticles is a promising route to control the dissolution and environmental pH value of CS bioceramics.