Infrared to visible frequency upconversion fluorescence spectroscopy in high Er3+-doped AlF3-based fluoride glass, excited at 800 nm, is experimentally investigated. In AYF glass, the optimum Er3+ content for 550 nm emission is about at 6% mol ratio, which is 12% mol ratioin AZF glass. With the increasing of Er3+content, the intensity ratios of the red emission to the green emission (Ir/Ig) is increased in AYF and AZF glasses, and the red emission intensity in these glasses depends on (Pex)1.6. They are mainly due to a cross-relaxation process between two erbium ions, one in the 4S3/2 and the other in the 4I9/2.