The invention relates to a method for monitoring and measuring a full section of a tunnel through three-dimensional laser, and belongs to the field of tunnel engineering construction monitoring. The method comprises the following steps of: arranging target points in a tunnel to be measured according to a requirement; determining whether to adopt one-station scan or multi-station scan according to the monitoring length of the tunnel; erecting an instrument at a proper position and scanning the full section of the tunnel; after the scan is finished, importing data into a computer; registering point cloud data acquired through the scan to generate a three-dimensional model by applying three-dimensional data processing software; and generating a comparison model by combining a previous three-dimensional model for the same tunnel at different time, and selecting a specific section and characteristic points to generate a variation analysis chart and a variation analysis sheet for a corresponding position. By the method, the full section of the tunnel is monitored in real time, the speed and accuracy of monitoring and measuring work are improved, manpower and material resources are saved, the speed and quality for monitoring and measuring the tunnel are improved, and reliable guarantee is provided for tunnel engineering construction.