According to recent research statistics, approximately 30% of people who experienced falls are over the age of 65. Therefore, it is meaningful research to detect it in time and take appropriate measures when falling behavior occurs. In this paper, a fall detection model based on improved human posture estimation algorithm is proposed. The improved human posture estimation algorithm is implemented on the basis of Openpose. An improved strategy based on depthwise separable convolution combined with HDC structure is proposed. The depthwise separable convolution is used to replace the convolution neural network structure, which makes the network lightweight and reduces the redundant layer in the network. At the same time, in order to ensure that the image features are not lost and ensure the accuracy of detecting human joint points, HDC structure is introduced. Experiments show that the improved algorithm with HDC structure has higher accuracy in joint point detection. Then, human posture estimation is applied to fall detection research, and fall event modeling is carried out through fall feature extraction. The designed convolution neural network model is used to classify and distinguish falls. The experimental results show that our method achieves 98.53%, 97.71% and 97.20% accuracy on three public fall detection data sets. Compared with the experimental results of other methods on the same data set, the model designed in this paper has a certain improvement in system accuracy. The sensitivity is also improved, which will reduce the error detection probability of the system. In addition, this paper also verifies the real-time performance of the model. Even if researchers are experimenting with low-level hardware, it can ensure a certain detection speed without too much delay.