Abstract: Green hydrogen is produced by water electrolysis technology with renewable energy as energy supply. In order to achieve the goal of carbon neutrality, the raw material hydrogen in chemical industry can be partly replaced by green hydrogen. At present, among all kinds of water electrolysis technologies, hydrogen production by alkaline water electrolysis technology is suitable for chemical processes. For large-scale application of alkaline hydrolysate in chemical production, the safety and economy are determined by the hydrogen to oxygen (HTO), a key index of plant operation. In order to predict the HTO value, the basic electrolytic water system was modeled by HYSYS. Pearson correlation analysis was used to select seven relevant variables as inputs for the data generated by HYSYS. The gas purity prediction model based on principal component analysis and artificial neural network (PCA-ANN) was developed. The MAE (Mean Absolute Error) value is 0.2030, MSE (Mean Square Error) value is 0.0956, R² is 0.7154, and R² of the model can reach 0.9507 after optimizing the abnormal data of boundary conditions.