Upper-lower staggered composite wood beam systems are widely preferred by architects for long-span glulam roof structures. However， the mechanical characteristics of its connections remain unclear. Using the large-span roof structure of the Yixing Art Museum as the engineering background， an innovative joint configuration is proposed， in which a cross-shaped steel plate in conjunction with self-tapping screws connects the upper and lower staggered composite timber beams. Shear performance tests were conducted on composite beam joints. The test results show that using cross-shaped steel plates and self-tapping screws at the composite beam， joint interfaces can effectively enhance the shear capacity between interfaces. The load-displacement behavior of the test joints presents three distinct stages： elastic stage， nonlinear stage， and yield stage. The average ultimate shear capacity and initial stiffness of the specimens were 218.5 kN and 35.4 kN/mm， respectively. The typical failure modes included screw yielding and local crushing of wood fibers around the screws， indicating a ductile failure mode. Furthermore， the Foschi model effectively predicts the mechanical behavior of the proposed composite beam joints.