To address issues such as low detection accuracy and the occurrence of missing or misidentifying bovine faces due to their small size, we propose an enhanced model called Mask R-CNN+MResNet. Firstly, we introduce a MResNet network based on the ResNet101 architecture, which enhances the detection accuracy of the model by improving upon ResNet101. Secondly, we adjust the anchor frame size of the model′s RPN network to enhance its capability in detecting small targets. Experimental results demonstrate that compared to the original network model, MResNet achieves a 12.6% improvement in bovine face detection accuracy. Furthermore, the improved model exhibits a 2.4% increase in average accuracy for detecting small targets, compared to the original model. These results indicate that this model effectively detects small target cow faces and holds practical application value.