To harvest kinetic energy, it is highly desirable to use flexible piezoelectrics. From environmental point view, renewable materials would be better to be used. Cellulose from biomass, among which cellulose nanocrystal (CNC) is piezoelectric and transparent, is renewable. In this study, a unique process is developed to fabricate polymer-CNC piezoelectric composites. The polymer-CNC composites with different compositions were prepared using the process. When the PVDF-based piezoelectric polymers are used, it is experimentally found that adding CNC can improve/enhance its insulation performance, dielectric and piezoelectric properties.