The mobile diffrential optical absorption spectroscopy(DOAS) instrument uses a telescope to collect zenith scattered light in the UV or visible region and it was used to derive the vertical column density of trace gases above the measurement route. However, the slant column density are retrieved instead of vertical column density recently, which results in emission flux computing error. Combined with the MAX-DOAS, a mobile multi light DOAS system, which set two different elevation angle telescopes(90, 30) to receive the scattered light respectively in the mobile platform, was deployed. The slant column density in the two different viewing directions were detected, and combined with the air mass factor computing from radiative transfer model, the vertical column density of trace gas was obtained. Comparison of the current mobile single light (zenith direction) DOAS system, the mobile multi light DOAS system have a lot of advantages like high sensitivity, low uncertainty etc. A test experiment was performed in a power plant of Huainan, Anhui using the new technique. The distribution information of NO2 vertical column density along the route was derived and compared with the slant column density calculating from the zenith direction, a good agreement was found in the column density trends.