Abstract: 304L stainless steels with two different grain size were fabricated by cold rolling and annealing at 900℃ and 700℃, respectively. The effect of grain size on room-temperature and high-temperature tensile properties of the steels was studied. The results show that the annealing treatment made the cold-rolled elongated grains recrystallize to form equiaxed grains. When the annealing temperature was 900℃ and 700℃, the average grain size was 63 μm and 3 μm, respectively. During tension at 25℃ and 200℃, the yield strength of the test steel with fine grains was higher than that of the test steel with coarse grains, but the percentage elongation after fracture was lower than that of the test steel with coarse grains. When the tensile test temperature increased to 800℃, the tensile fracture of the two grain size test steels both exhibited a transgranular+intergranular mixed fracture mode, indicating the grain boundary did not play a significant strengthening role; therefore, the strength and percentage elongation after fracture of the two grain size test steels stretched at 800℃ were basically the same.