The invention relates to the technical field of solar geometrical optical efficiency measurement, and particularly relates to a CPC convergence rate measurement device used for a linear Fresnel type light concentrating system and a method thereof. The measurement device comprises a CPC fixing framework, a measured CPC, flexible thin-film solar cell bare chips and heat collecting tubes. The flexible thin-film solar cell bare chips are wound on the heat collecting tubes. The CPC fixing framework is provided with a polished rod framework which is provided with a pulley and a laser device. The pulley is connected with a stepping motor through a synchronous belt and a synchronizing wheel. The stepping motor drives the pulley to move. The measured CPC convergence rate under different incident angles can be accurately calculated by establishing detection equipment so that average convergence rate can be obtained. The average convergence rate directly determines whether the CPC convergence rate is reasonable for enhancing photothermal conversion efficiency and evaluating arrangement of the vacuum heat collecting tubes and guides work personnel to regulate the angle and the position, and the angle and the position of the vacuum heat collecting tubes are continuously measured and corrected by the detection equipment so that the vacuum heat collecting tubes are ensured to receive more solar rays and thus product work efficiency can be greatly enhanced.