Three-dimensional photonic crystals (PCs) composed of polystyrene (PS) spheres are fabricated by the self-assembly method, and the transformation of the PC structures from ordered to disordered is carried out via mixing larger silica spheres in the suspension of PS spheres with different concentrations. By measuring and analyzing the tranmission and reflection properties of these samples, the sharp declination of transmittance in the high frequency range, the disappearance of Fabry-Pérot oscillations in the low frequency region, the blue-shift and the gradual disappearance of the photonic band gaps of PCs with the degree of disorder increasing are observed. When the concentration of doped spheres is declined to 0.02%, the lowest transmittance at the center position of photonic band gap decreases from 10% to 1% and the single peak in the reflection spectrum is split into two peaks. These will contribute to the achievement of better transmission extinction of the three-dimensional PCs composed of dielectric spheres along the Γ-L direction as well as to promote their development in the field of new optical devices.