The invention relates to an ultrasonic automatic splicing machine of polyester base cloth in a membrane production line, and particularly relates to a device for automatically splicing polyester base cloth in the membrane production line through the adoption of an ultrasonic technology. The polyester base cloth is in a mode of ultrasonic welding, and a series of automatic measurements are adopted to realize a series of automatic operations, such as automatic feeding, automatic recognition, automatic cutting, automatic lapping, and automatic fusing, on the polyester base cloth, and the joint in a reel of the base cloth can be automatically processed, the joint is cut and automatically spliced and fused, and then the base cloth can enter a working state without manual intervention.