Twenty-two soybean lines(MS-01 – MS-22)harvested in the fall of 2014 in Stoneville,MS were selected for filled-tofu making in order to analyze the correlation of protein subunit content and tofu firmness.Filled tofu making and breaking stress analysis demonstrated a significant correlationship of A3 subunit content and firmness of filled tofu.The result suggested that the soybean A3 subunit could be used as an effective marker for predicting the firmness of tofu in the soybean breeding program.