To understand the effect of polarization effect of the imperfect lens components and angle error of linear polarizers on polarimetric precision of the aerosol polarimeter, firstly, the polarization degree of lens component is deducted by combining the Jones matrix of lens component with the coherent matrix of incident beam. Secondly, the polarimetric error of the instrument is estimated by using Mueller matrix, considering all effects of the polarization states of incident beam, polarization effect of lens component and the azimuth errors of polarizers. Finally, the polarization degree of lens components and the polarimetric error of the instrument are specifically computed, respectively. At the channel of 0.67 μm, the maximum of polarization degree of the lens component and absolute polarimetric error of the instrument are 0.3143 and 0.2838, respectively. At the channel of 1.64 μm, the maximum of polarization degree of the lens component and absolute polarimetric error of the instrument are 0.3249 and 0.2937 respectively. It is indicated that the major error of the polarimeter arise from polarization effect of the imperfect lens components and a great error exists if the instrument is not calibrated.