In recent years, with the rapid development of fluorescence imaging technology, there has been an increasing demand for detection. Super resolution fluorescence microscopy, by repeatedly activating and quenching fluorescent molecules to break through diffraction limits, combined with fluorescent labeling, can achieve nanoscale imaging and quickly and accurately detect human diseased cells. Therefore, it is widely used in the field of medical detection. Traditional dichroic mirrors mainly play a role in separating spectra in optical systems, while in fluorescence imaging optical systems, the performance of dichroic mirrors not only needs to consider spectral performance, but also the reflection wavefront distortion (also known as surface flatness PV) of the device. When the surface flatness of the device is poor, that is, when the PV value of the reflected wavefront distortion test result is large, phenomena such as “defocusing”, “astigmatism”, focal plane separation, and blurred spot size can occur after passing through the dichroic mirror. This problem causes the optical system to be unable to accurately distinguish cell structures at the nanoscale, thereby limiting the imaging results of the detection system. The reason for the poor surface flatness of the device is that during the deposition of multi-layer optical films, the surface flatness of the optical device can change under the action of film layer stress, resulting in changes in the surface shape of the coated product. Therefore, there is an urgent need to develop low wavefront dichroic filter devices. This article studies the effect of substrate resistance to thin film stress and finds that the stress change of thin films deposited on JGS1 is smaller than that on K9. Therefore, JGS1 is selected as the experimental substrate; by studying the effect of annealing temperature on the stress of Ta₂O₅, Nb₂O₅, and SiO₂ material film layers, it is found that as the annealing temperature increases, the stress of Ta₂O₅ material film reverses from compressive stress to tensile stress, while the stress of Nb₂O₅ and SiO₂ materials remains in compressive stress. It was proposed to achieve low wavefront distortion by canceling out the positive and negative stresses of the film layer. Ta₂O₅ and SiO₂ materials were selected as high and low refractive index materials, and the relationship between the film thickness ratio and annealing temperature at the time of stress cancellation of the two materials was inversely fitted. According to the relationship, it can be seen that the film thickness ratio of Ta₂O₅ and SiO₂ materials needs to be at least greater than 2.6∶1. After preparation, annealing can achieve stress reduction. Force offset; based on the fitting results, the film structure was designed and adjusted. The physical film thickness ratio of the two materials was controlled by changing the optical thickness of the high refractive index material while ensuring that the spectrum was met. The physical film thickness ratio of Ta₂O₅ material and SiO₂ material was designed to be 4.3∶1. Finally, the optical thin film was prepared by sputtering deposition, and the reflection wavefront distortion was further optimized by gradually increasing the annealing temperature. Finally, a dual band low wavefront distortion dichroic mirror was prepared. After testing, a 2 mm thick quartz substrate was used, and the spectral test results show thatthe T_avg>97%@504~544 nm & T_avg>97%@588~800 nm, T_abs<2%@450~491 nm & T_abs<2%@556~566 nm, the wavefront distortion (reflected PV value) test result is 0.087 λ, and it has passed the environmental durability test.