A large work area framing image tube with magnetic lenses is designed. By theoretical analysis and analog simulation, the characteristics of spatial resolution in different off-axis positions of framing image tube with single lens and treble lenses are studied. Experiments are also conducted to verify the results. In the simulation, when the imaging demagnification is 21, the single lens structure can reach 5 lp/mm spatial resolution within 10 mm off-axis radius, while the treble lenses structure can reach 5 lp/mm spatial resolution within 30 mm off-axis radius. In the experiments, the single lens structure can reach 5 lp/mm spatial resolution within 12 mm off-axis radius, while the single lens structure can reach 5 lp/mm spatial resolution within 27 mm off-axis radius. The results show that by using the framing image tube of treble lenses structure design, its effective detection area is about 4 times as large as that of the single lens structure.