In a jet loom provided with a plurality of guide members disposed in an alignment on a sley to form a fluid and weft guide passage, a fluid jetting main nozzle directed to said guide passage and a transfer valve which is connected to the main nozzle so that at the filling time a flow of compressed fluid is started to the main nozzle and a volume of a compressed fluid is accumulated between the main nozzle and the transfer valve, and a fluid is jetted from the main nozzle, and after the filling operation, jetting of the fluid is stopped, the improved filling method comprising jetting the fluid from the main nozzle at the filling time, stopping the flow of compressed fluid to the main nozzle after the elapse of the time necessary for the filling operation, and simultaneously discharging the compressed fluid accumulated between the transfer valve and the main nozzle, whereby the fluid pressure in the main nozzle is promptly reduced.