A gaseous nitrous acid (HONO) prediction model based on Stacking ensemble learning was proposed. The concentrations of HONO in Beijing urban area were obtained using incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS). Combined with the HONO sources, O₃, CO, SO₂, NO, NO₂, NO_y, temperature (T), relative humidity (RH), wind speed (WS), j(HONO), j(NO₂), j(O¹D) were selected as characteristic data. By analyzing the average diurnal variation of HONO, the measurement time was converted into a new feature hour by hour. The base model was constructed by utilizing Extreme Gradient Boosting (XGBoost), Light Gradient Boosting Machine (LightGBM) and Random Forest (RF) algorithm. The training set was partitioned by 5-fold cross-validation method. The output of the base model was taken as a new feature set and as the input of second-level linear regression model. HONO prediction model was finally obtained via training the models in these two layers. Through the feature importance analysis and calculating the contribution of direct emission of vehicles at night, it showed that CO was an important impact factor in the prediction model, and that the direct emission of vehicles was a major source of HONO in the winter period at the region. The prediction performance of the base model and the Stacking ensemble model were evaluated by the test set respectively. The correlation coefficients between forecast results and measured values for the three base models were above 0.91. The performance of the Stacking ensemble model was the best, whose correlation coefficients reached 0.94. The average absolute error and root mean square error were 0.307×10^-9 and 0.453×10^-9, respectively. Explanability and applicability of the HONO prediction model based on Stacking ensemble learning.