Due to the limitation of observation method in cell factory (1~40 layer dishes) monitoring in China, this paper designs a long-working-distance video objective for observing the cultured cells in cell factory, to facilitate the observation, save time and improve efficiency. According to the size of cells, the high resolution video objective, with 5 times magnification and 85 mm working distance, is designed by applying ZEMAX stimulation and Cassegrain reflector system. Amplified again by the video display, the total magnification is about 200 times, the numerical aperture is up to 0.3 and the liner field object height y is 0.6 mm, equipped with MV-200UC 1/3″ charge couple device (CCD) produced by Microvision in observation. The minimum distance resolution of the system is about 1.1 μm, meeting the requirement of distinguishing petri dish cells.