Aiming at the problem of UAV aerial photography parameters relying on manual experience when collecting image of 3D real scene reconstruction at traffic accident sites，which led to large model measurement errors and low precision，an automatic calculation method of key parameters of UAV aerial photography was proposed. First，the key parameters of aerial photography used by single-lens UAV for images acquisition of traffic accident site were altitude，gimbal angle and shooting interval angle. The numerical relationships of the key parameters with the imaging range，imaging accuracy and overlap rate were analyzed. Then，the aerial photography key parameters computation model was constructed. The key input parameters were the given accident site，UAV technical parameters，image aspect ratio and overlap requirements. On the premise that the accident site was in the effective imaging range and there was no imaging blind zone，the UAV photography parameters were automatically calculated with the goal of improving the accuracy and presentation effect of the image utilization rate model. Finally，combined with case application，the UAV aerial photography parameters calculated by this method were applied to complete the image acquisition at the accident sites，and the constructed 3D real scene model could clearly and completely present the overview of the accident site，with an average measurement error of 1.72%，and a measurement accuracy of 3.54 cm. Compared with the manual empirical method，the average error of the method was reduced by 47.56%，and the accuracy was improved by 48.40%. The study shows that this method can realize the automatic quantitative calculation of aerial photography parameters for 3D real scene reconstruction of traffic accident sites，construct the model with centimeter-level error，and improve the parameterization and automation of UAV aerial photography.