Photoelectron spectroscopy is a powerful tool in characterizing the electronic structure of materials. To investigate the specific region of interest with high probing efficiency, in this work we propose a compact in situ microscope to assist photoelectron spectroscopy. The configuration of long objective distance of 200 mm with two-mirror reflection has been introduced. Large magnification of 5× to 100×, lateral resolution of 4.08 µm, and longitudinal resolution of 4.49 µm have been achieved. Meanwhile, the testing result shows larger focal depth of this in situ optical microscope. Similar configurations could also be applied to other electronic microscopes to improve their probing capability.