Abstract: The multi-mode instrument means one instrument with several observational functions.The first one in the world-EFOSC was developed by ESO in 1984.It's outstanding advantages hold interest for astronomers and some similar instruments are now commonly used.A proposal for the multi-mode instrument YFOSC (Yunnan Observatory faint object spectrograph and camera) attached to the 2m telescope at the Gaomeigu Station is described,which includes the function requests,the construction,the main parameters,the observational capabilities,and the control system. The first function is focus reducer with 3/f and field view of 10′.The second can be used is a stellar coronagraph with opaque spots of 1″,1.5″,2″,......8″.The polarimeter mode is employed to measure the Stokes parameters.YFOSC offers spectroscopic function with low and moderate resolutions.The detectable magnitudes are estimated for each observational mode.Some parameters and filters are considered.