This paper presents a hybrid multi-order diffractive lens that supports dual-band computational imaging in both visible and mid-wave infrared (MWIR) bands. By applying diffraction structures of varying depths on both sides of the same substrate and optimizing these structural parameters using the end-to-end optimization framework, we successfully developed a diffractive element capable of efficient focusing in the visible light band (640~800 nm) and the MWIR band (3700~4700 nm). Coupled with a specially designed image reconstruction network, this approach realizes a monolithic dual-band computational imaging system with simplicity, lightweight construction, and low cost. Experimental results show that the prototype with a diameter of 40 mm achieves static modulation transfer functions of 50.0% in the visible light band and 4.4% in the MWIR band. Under room temperature conditions, the noise equivalent temperature difference in the infrared band does not exceed 80 mK, confirming the effectiveness and practicality of the proposed design.