In order to study the mechanical properties of mechanically connected nodes of double-web I-beam GFRP girders, based on static load tests of two types of glass fiber reinforced polymer (GFRP) girders without and with mechanical connections, the force characteristics of double-web I-beam GFRP girders under symmetric loading at three points were analyzed, and the limit states and damage forms of the two types of girders were clarified. The results show that the GFRP waist beam adopts double web I-beam cross-section type, and the maximum stress of the cross-section is 183 MPa, which is 62% of the longitudinal tensile strength and 73% of the longitudinal compressive strength of the GFRP waist beam (205% of the allowable compressive load capacity), which can make the GFRP material strength fully developed and the waist beam has good stability performance. GFRP waist beam is prone to local damage, firstly, local instability occurs at the flange plate, which then causes buckling damage to the web, surface peeling and bulging at the connection of flange and web, and the additional splice plate and bolts at the connection of waist beam can effectively suppress the local damage deformation. Adopting bolt mechanical connection and adding the same material splice plate at the connection can reduce the weakening effect of bolt drilling on the cross-section of the beam itself, so that the stiffness and ultimate bearing capacity of GFRP waist beam can be increased by 17.9% and 44.9% respectively, which is a reasonable connection method for GFRP waist beam. The research results can provide reference and reference for the promotion and application of GFRP girders.