The invention relates to a magnesium alloy ventilation window of a railway coach and a manufacturing process thereof. The manufacturing process comprises preparation of mixed rare earth modified magnesium alloy ingots, hot extrusion and cutting of thin-walled sectional materials with different specifications and small cross sections, argon arc welding of an magnesium alloy frame, assembly and surface treatment. The magnesium alloy for manufacture of the magnesium alloy ventilation window is mixed rare earth modified magnesium alloy, mixed rare earth is cerium-rich mixed rare earth and is composed of 60-65 percent of Ce, 25-30 percent of La, 5-10 percent of Pr and 1-2 percent of Nd; the total content of the mixed rare earth in the magnesium alloy is 0.1-1.5 percent; the magnesium alloy frame, magnesium alloy fan blades and magnesium alloy sleeve rings are all made of extruded thin-walled magnesium alloy sectional materials with small cross section; and the wall thickness is 2-3mm. The invention can play an important role in the process of speeding up the development of the light-weighted railway coach.