To enhance the accuracy of deep learning models in simulating watershed runoff under changing environmental conditions, a coupled model of convolutional neural network (CNN), long short-term memory (LSTM) and Attention mechanism was constructed for the study of the Qinhe River Basin. Integrated with multiple optimization algorithms and multiple scenarios in BCC-CSM2-MR climate model from the Coupled Model Intercomparison Project Phase 6 (CMIP6), this model was applied to watershed runoff simulation and prediction. Its simulation accuracy was then compared with that of various deep learning models. The results demonstrate that the CNN-LSTM-Attention model exhibits superior performance in simulating runoff in the Qinhe River Basin, with Nash-Sutcliffe efficiency coefficient (NSE) of 0.883, root mean square error (RMSE) of 2.317, and mean absolute error (MAE) of 1.098, outperforming other deep learning models. Notably, the annual runoff of the Qinhe River Basin from 2025 to 2050 shows a slow decreasing trend with significant fluctuations under different climate change scenarios, especially in the SSP1-2.6 scenario. This study provides new insights into the application of deep learning models in intelligent simulation of human-water relationships and offers a referential value for subsequent water resources development and management in the watershed.