The invention discloses a full-automatic comprehensive detector for size of front end of a tank. The full-automatic comprehensive detector for the size of the front end of the tank comprises a workbench for placing a tank body, a data processing device, a conveying device for conveying the tank body, a tank clamping device for clamping and replacing the tank body, a fixing device for fixing the tank body, a first measuring device for measuring the height and the wall thickness of the tank body, and a second measuring device for measuring the depth of a bottom arch, wherein the first measuringdevice is arranged at the upper part of the tank body and is vertical to the workbench; the second measuring device is arranged at the bottom of the tank body; and detection information of the first measuring device and the second measuring device is processed by the data processing device and then displayed. The device is capable of automatically measuring data such as the tank body height of twotanks, tank body wall thickness, and the arching degree of depth; the conveying and the tank clamping device are provided to meet the detection to a plurality of measured data of two tanks in the production detection; in addition, operators do not replace and fill the tank body; the size of the tank can be automatically detected, thus the working efficiency is improved, and the input cost is decreased.