<p>We carried out 19 city-circle-around car MAX-DOAS experiments on the 6th Ring Road of Beijing in January, September, and October 2014. The tropospheric vertical column densities (VCDs) of NO<sub>2</sub> were retrieved from measured spectra by the Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) technique and used to estimate the emissions of NO<sub><i>x</i></sub> (≡ NO + NO<sub>2</sub>) from urban Beijing during the experimental periods. The offline LAPS-WRF-CMAQ model system was used to simulate the wind fields by assimilation of observational data and calculate the NO<sub>2</sub>-to-NO<sub><i>x</i></sub> concentration ratios, both of which are also needed for the estimation of NO<sub><i>x</i></sub> emissions. The NOX emissions in urban Beijing for the different seasons derived from the car MAX-DOAS measurements in this study were compared to the multi-resolution emission inventory in China for 2012 (MEIC 2012). Our car MAX-DOAS measurement results showed higher NO<sub>2</sub> VCD in January than in the other two months and typically larger NO<sub>2</sub> VCD at the southern parts of the 6th Ring Road than at the northern parts. The wind field had obvious impacts on the spatial distribution of NO<sub>2</sub> VCD, with the mean NO<sub>2</sub> VCD along the 6th Ring Road typically being higher under the south wind than under the north wind. In addition to the seasonal difference, the journey-to-journey variations of estimated NO<sub><i>x</i></sub> emissions rates (E<sub>NO<sub><i>x</i></sub></sub>) were large even within the same month, mainly due to uncertainties in the calculations of wind speed, the ratio of NO<sub>2</sub> and NO<sub><i>x</i></sub> concentration, and the decay rate of NO<sub><i>x</i></sub> from the emission sources to the measured positions under different meteorological conditions. The ranges of E<sub>NO<sub><i>x</i></sub></sub> during the heating and non-heating periods were 28.7 × 1025 to 60.0 × 1025 molecules s<sup>−1</sup> and 7.7 × 1025 to 24.8 × 1025 molecules s<sup>−1</sup>, respectively. The average E<sub>NO<sub><i>x</i></sub></sub> values in the heating and non-heating periods were 43.0 × 1025 molecules s<sup>−1</sup> and 13.9 × 1025 molecules s<sup>−1</sup>, respectively. The uncertainty range of E<sub>NO<sub><i>x</i></sub></sub> was 16.4–33.2 %. The monthly emission rates from MEIC 2012 are found to be lower than the estimated ENOX, particularly in January. Our results provide important information and datasets for the validation of satellite products and also show how car MAX-DOAS measurements can be used effectively for dynamic monitoring and updating of the NO<sub><i>x</i></sub> emissions from megacities such as Beijing.</p>