On the basis of a series of hyperbranched conjugated polymers (HPV) synthesized in our laboratory, the composition of HPV with nanosized cadmium sulfide (CdS) particles is investigated by means of static and dynamic fluorescence spectroscopies and atomic force microscopy (AFM). The apparent association constant between HPV and CdS can be obtained from the plot of the relative fluorescence quantum yields versus the reciprocal concentrations of CdS. The electron injection rate from excited HPV to the conduction band of CdS can also be calculated. Both the constant and the electron injection rate are related to the chain length of the alkoxy group on the connecting modules, leading to the conclusion that the modification of HPV at certain substitution sites can control the interaction between HPV and nanosized CdS particles. The CdS particles with different surface charge may result in significant changes of the apparent association constants, which shows that the electrostatic force probably plays a key role in the combination of HPV with CdS. AFM images indicate that films with good qualities can be formed on a mica substrate using the composite of HPV with nanosized CdS particles. The presence of HPV can decrease the self-aggregation of cadmium sulfide particles.