Because the fluorescence signal induced by a cancer cell is weak and has a wide spectral range, along with the detection limits of existing microscopes, this paper proposes fluorescence microscope objectives with a spectral range of 450—800 nm and a numerical aperture of 0.95. The objective used “+ + -” structure because the correction of aberration, caused by a wide spectrum and high numerical aperture, is difficult. The objective must include a set number of lenses and the alignment process is difficult; the front group, considering more than 90% focal power, is set as the sensitive component, which is useful for adjusting the alignment process; the middle group is the weak focal component, which is used to correct the secondary spectrum caused by the large numerical aperture, so that the difficulty in manufacturing the apochromatic elements is reduced significantly. The posterior group is the negative component, which is useful for flattening the image field and increasing the working distance of the objective. The objective parameters are as follow: the total length is 58 mm, the working distance is 0.21 mm, the magnification is 40×, and the full field is 0625 mm. The results show that the image quality nearly reaches the diffraction limit and the distortion is less than 0.2%, meeting the surveilling requirements of the weak fluorescence signal from cancer cells.