We have demonstrated a high power red fiber laser with a Pr-doped waterproof fluoro-aluminate glass fiber (Pr:WPFGF). When 800 mW pumping power of a blue/violet GaN laser diode (GaN-LD) was launched into the Pr:WPFGF (core diameter 8 μm, length 40 mm) with dielectric coating on both end surfaces to construct a resonator, the maximum output laser power at 638 nm was obtained to be 311.4 mW that is higher than previously reported Pr:ZBLAN fibers. The threshold power was evaluated to be 52.1 mW, and the slope efficiency was calculated to be 41.6%. Assuming the resonator to be a Fabry-Perot resonator, we can calculate the output power to be 336 mW at 800 mW pump power and the slop efficiency to be 44.2%. These theoretical values show good agreement with experimental ones.