Optical splitting film-based spectral splitting concentrated photovoltaic thermal system (CPV/T) utilises the full spectrum of sunlight to obtain more useful energy and enables the PV cells and thermal absorber work at different temperature. In this work, an optical splitting film-based spectral splitting CPV/T under concentrated solar irradiance was devised and set up to utilise the full spectrum sunlight and decrease the temperature of CPV cell. The reflection bands of SiO2/TiO2 interference thin film matched well with the spectral response bands of the CPV cell, which could avoid the infrared light to heat CPV cell. Under concentrated solar irradiation, temperature of CPV, photoelectric and photothermal conversion efficiencies were tested. The overall energy and exergy conversion efficiencies were theoretically analysed. The results showed that the CPV cell with optical splitting film could reduce by 11.0 K, and power generation and photoelectric conversion efficiency of the CPV cell could improve by 9.4% and 1.3% under concentrated solar irradiation, respectively. The overall energy and exergy conversion efficiency of proposed system could achieve 18.85% and 14.61%, i.e., 5.8% and 1.5% higher than those of the CPV system without film under concentrated solar irradiation, respectively.