The invention discloses an adjustable carton packaging machine convenient to convey, and relates to the technical field of carton packaging. The adjustable carton packaging machine comprises a rack, wherein a conveying roller and a carton sealing device are arranged on the rack, the conveying roller is used for conveying a carton located on the conveying roller, the carton sealing device is used for sealing the carton through an adhesive tape, an opening is formed in the middle of the rack, a conveying device is arranged at the bottom of the rack at the opening, and the conveying device comprises a driving mechanism and a clamping mechanism. According to the adjustable carton packaging machine, when the carton moves to the position between two clamping blocks in the same group located above the opening, a conductive spring is electrified, the conductive spring is electrified and contracted, two sliding frames are pulled to be close to each other, then the two clamping blocks form a clamping effect on the carton, so that the carton is prevented from fluctuating in the transportation process, meanwhile, the carton packaging machine can be effectively adapted to cartons with different specifications and the length smaller than the initial distance between the two clamping blocks, and the adaptive conveying and packaging effect on express cartons with different specifications can be formed.