In the present investigation, a series of P(VDF-HFP)-based composite gel polymer electrolyte membranes using silica aerogel (SAG) as filler have been synthesized with varying the plasticizer-filler ratio, systematically. The maximum room temperature ionic conductivity is found to be 1.04 x 10(-2) S/cm. XRD and FTIR studies have been conducted to investigate the structural and interaction of different groups in the composite polymer electrolyte (CPE) membrane. Microstructural studies by SEM exhibit highly porous membrane due to presence of silica aerogel particles. DSC results confirm that with the addition of SiO2 aerogel up to 4 wt.%, the glass transition temperature (T-g) and crystallinity decreases, but increases slightly when it crosses this limit.