Calcium copper titanate (CaCu3Ti4O12, CCTO) particles with three types of particle size (CCTO–i, CCTO–ii, CCTO–iii) areprepared by wet chemical method. And then the dielectric composites based on CCTO particles and Phenol formaldehyderesin (PF) are fabricated by mixing and mould pressing. This paper mainly studies the microstructure and dielectric propertiesof CCTO/PF dielectric composites (CCTO–i, CCTO–ii and CCTO–iii composites). XRD, FTIR and SEM indicate that theCCTO particles are dispersed in the polymer matrix. In addition, the effect of particle size on the dielectric properties ofCCTO/PF composites is also discussed. By comparing the CCTO/PF composites with different particle sizes, it is found thatthe CCTO–i composite has a high maximum dielectric constant and low loss at room temperature of 100 Hz, while the CCTOvolume fraction was 0.5 in the measurement frequency range, which shows a very weak frequency dependence. On this basis,the CCTO–i composite with relatively small particle size has excellent dielectric properties, which may imply that the effectof interface will be changed by smaller particle size.