This paper studies the steady state luminescent behavior of Yb3+Er3+ codoped and Er3+ mono-doped oxyfluoride vitroceramic mater ials.The cross-energy-transfer effect between Yb3+ and Er3+ ions in oxyfluoride vitroceramics(FOV)，oxyfluoride glass(FOG) and fluoride gl ass(ZBLAN) materials have been studied carefully also.Some new luminescence phen omenon is found,as described in the following.When the4G11/2 level of Er-doped FOV is excited by 377nm ultraviolet light，there appear a very strong green 4S3/2→4I15/2 fluo rescence and a middle strong red 4Ｆ9/2→4I15/2 fluorescence.However, when the 4G11/2 level of ErYb-codoped FOV is excited by 377nm ultraviolet light，the red4Ｆ9/2→4I15/2 fluorescence is increased about ten t imes, and meanwhile the green 4S3/2→4I15/ 2 fluorescence is decreased about 100 times.The variation of the red-green light ratio is about 1000 times.This interesting phenomenon exists only in FOV but not in FOG and ZBLAN.This paper also discuss how to apply this effect to th e Fluorescence Guard-Against-Forge in practice.