The invention relates to a rear panel composite film for a solar photovoltaic cell assembly, and a preparation method for the rear panel composite film. The rear panel composite film for the solar photovoltaic cell assembly is formed by compounding a polytetrafluoroethylene (PTFE) rotary cut film (1) with thickness of 0.028 to 0.040mm, a polyethylene terephthalate (PET) film (2) with the thickness of 0.17 to 0.35mm, a PTFE rotary cut film (3) with the thickness of 0.028 to 0.040mm, and hydrophilic films a, b, c, and d, wherein the hydrophilic films a, b, c, and d are arranged on upper and lower surfaces of the PTFE rotary cut film (1) and the PTFE rotary cut film (3). The preparation method comprises the following steps of: coating adhesives on the upper and lower surfaces of the PET film respectively, arranging the PET film between the PTFE films and the hydrophilic films, hot-pressing, and bonding and curing to obtain the rear panel composite film. Import raw materials are not used in the rear panel composite film, so cost is greatly reduced, and domestication degree is improved. Moreover, the rear panel composite film can be adhered to a glue film of a solar photovoltaic cell well.