The invention provides a crowd statistics method and a system based on video monitoring. The method comprises the following steps: S1, a real-time monitoring image in a pre-monitoring area is acquired; S2, foreground segmentation is carried out on the real-time monitoring image, and a crowd is segmented; S3, a complete human body feature model is divided to five local feature models, and a corresponding weight is configured for each local feature model; S4, features of the crowd after segmentation are extracted, matching detection is carried out with the five local feature models, the comprehensive matching degree is calculated according to the weight and the extracted position offset between the five local feature models and the complete human body feature model, and if a specified threshold is exceeded, matching succeeds; and S5, according to the successful matching times, crowd statistics is carried out, a crowd number change curve is drawn, and when the curve or the curve trend triggers an abnormal event, warning is carried out. The crowd statistics method and the system based on video monitoring can be applied to different situations, and the accuracy is high.