Abstract: The core-shell structured hybrid particles with polystyrene (PS) as the core and SiO₂ nanoparticle as the shell were synthesized via electrostatic interaction based on the opposite charges. The SiO₂ shell thickness of the obtained hybrid particles could be tuned by varying the concentration of tetraethylorthosilicate. The atomic force microscope (AFM) was employed to probe the mechanical properties of the as-prepared samples. The compressive elastic modulus of the sample was measured by analyzing the force curves captured on the particle samples according to the Hertz contact model and Sneddon contact model. As confirmed by scanning electronic microscopy (SEM) and transmission electron microscope (TEM), the size of the PS core is (197±9) nm and the SiO₂ shell which is 11-16 nm in thickness in the test is composed of a lot of tiny particles. Under the condition of Hertz contact model, the elastic modulus of the PS microspheres is (2.2±0.5) GPa. The modulus of the PS-SiO₂ hybrid particle increases with the increase of the thickness of SiO₂ shell. When the shell thickness increases from 11 nm to 16 nm, the elastic modulus of the composite grows from (4.4±0.6) GPa to (10.2±1.1) GPa. The elastic modulus of the composite is much lower than that of the silica, and is more close to the modulus of the PS core.