The invention discloses a self-adaptive plate equal-length machining mechanism for constructional engineering. The self-adaptive plate equal-length machining mechanism comprises limiting clamping plates, a connecting mechanism, positioning supporting plates, a transmission mechanism, a building plate, a connecting roller, a connecting swing rod, a mounting support, a positioning mechanism, supporting legs, a material guiding inclined plate, a supporting table, protective clamping plates, connecting supporting plates, a connecting motor, an adjusting mechanism, a tooth-shaped belt, a fixed belt wheel and mounting clamping seats. The four groups of supporting legs used for supporting are uniformly and fixedly mounted on the lower end face of the supporting table at equal distances. According to the self-adaptive plate equal-length processing mechanism, a connecting groove is formed in the outer portion of a connecting disc, one part of the connecting disc can be connected with a gear disc in an engaged manner, the part, located in the connecting groove, of the connecting disc can carry out static positioning on the gear disc through grabbing clamping plates, then when the connecting disc is engaged with the gear disc, the building plate can be conveyed, when the gear disc is static, the connecting mechanism can cut the building plate, and the machining efficiency and precision to the building plate are effectively improved.