The invention relates to a transverse test device for a duct piece joint, comprising a left counter-force frame, a right counter-force frame, padding cushion blocks, multiple sets of force applying mechanisms, a hydraulic loading system and an electrical control system, wherein the left counter-force frame and the right counter-force frame are oppositely arranged and have same symmetrical structures; the padding cushion blocks are respectively plugged at two sides of the duct piece joint and between the left counter-force frame and the right counter-force frame; the duct piece joint is fixedly clamped between the left counter-force frame and the right counter-force frame; the multiple sets of force applying mechanisms are distributed on two sides of the duct piece joint to connect the left counter-force frame and the right counter-force frame and apply inward lengthways tension; the multiple sets of force applying mechanisms are controlled by the hydraulic loading system and the electrical control system to carry out loading on the left counter-force frame and the right counter-force frame to form a bending moment at the duct piece joint as shown in a formula of the description, wherein Ni is lengthways tension of various force applying mechanisms; Li is a transverse distance between all the force applying mechanisms and the duct piece joint; and I is the number of the force applying mechanisms. The transverse test device for the duct piece joint has the advantages of simple structure, strong adaptability and high accuracy, is suitable for duct piece joint transverse tests of various duct pieces in various working conditions, and is particularly qualified for the transverse test of the duct piece joint with a large bending moment.