NO2 vertical column density (VCD) is measured by direct-sun differential optical absorption spectroscopy (DS-DOAS). When cloud exists in the field of view of instrument, measurement results of this technique are influenced by multiple scattering of particles in cloud. To solve this problem, a new method is proposed. Simultaneously inversing O4 VCD is used to determine whether there is cloud in the field of view or not. Then the NO2 VCD is corrected. Statistics show that the variation amplitude of O4 VCD is 6% due to inversion error and atmosphere disturbance in cloud-free sky. If the magnitude of relative variation of O4 VCD is larger than 6%, there is cloud in the field of view. This method is used to correct NO2 results from a four-day field measurement. It is proved that this method can effectively improve the measurement precision of DS-DOAS when clouds exist in the field of view.