The invention discloses an automatic feeding system for steel tube cutting. The automatic feeding system for steel tube cutting comprises a bearing frame and a supporting platform. The bearing frame is located on the inner side of the supporting platform. The bearing frame is provided with a steel tube storage mechanism and a steel tube feeding mechanism. The supporting platform is sequentially provided with a horizontal material supply guide mechanism, a dimension adjusting mechanism and a locating and clamping mechanism from left to right. The horizontal material supply guide mechanism comprises a pushing mechanism and a guiding mechanism. Multiple Z-shaped material guiding plates used for feeding are arranged between the steel tube feeding mechanism and the horizontal material supply guiding mechanism. The upper end face of each Z-shaped material guiding plate is an inclined face. According to the automatic feeding system for steel tube cutting, the automatic mechanisms are arrangedin the steel tube feeding system to complete feeding and conveying of the steel tubes, so that full-automatic conveyance and locating are achieved in the steel tube cutting production process, and the difficulties and problems that in the manual steel tube conveying process, the conveying position is inaccurate, the labor intensity of workers is high and the environment is severe are solved; andthe product quality can be effectively improved, the number of workers needed in the production process is reduced, and the production efficiency is improved.