The invention discloses a method, device and system for monitoring a barrier in a hazardous chemical substance warehouse, and the method, device and system are used for achieving the real-time monitoring and early warning of the stacking safety distance of the hazardous chemical substance warehouse. The monitoring method comprises the steps: scanning a target warehouse, and obtaining the scanning data of the target warehouse; calculating the difference between the distances of two adjacent scanning points in the scanning data, filtering the noise points in the scanning points according to the distance difference, and obtaining a filtering result; determining that the adjacent scanning points which are not filtered as the barriers according to the filtering result, and obtaining the position information of the barriers. According to the technical scheme of the invention, the method can effectively remove the abnormal noise points in the scanning point cloud data through a denoising algorithm, can guarantee the integrity and reliability of normal point cloud data, and obtain the information of barriers in the target warehouse.