Lightweight structure is the trends in safety design of engineering machinery of rollover protective structures (ROPS). The lightweight remoulded ROPS of one wheel loader was loaded in side direction firstly, and then deformation analysis and research in time domain during lateral loading were carried out by using of strain gauge testing. The experimental results show that the lightweight remoulded ROPS, with the beam and the upright thinned by 5mm, connected with weld reinforcement and made of Q345B material can satisfy the needs of lateral loading capacity and energy absorption from ISO3471. When the lateral load reached the standard value, the energy absorption is just 30% of its standard one; when the energy absorption reached the standard value, the limit lateral loading capacity is 14 times of the standard one. The center of beam(W) where is near the loading position started plastic deformation firstly, with the approximate symmetric deformation on both sides of beam(W). The plastic hinge with “S” deformation is existed on beam(L). The upright(Z) where is near the loading position started plastic deformation firstly, but no plastic deformation below the center, with a stronger stiffness than that of beams.