A decoding method for determining a preferred survivor path in a decoding process is provided. The method includes calculating a first determination value of a first survivor path at a first time point, the first determination value being determined by a first sub determination value and a second determination value at a second time point, and the second time point being prior to the first time point; calculating a third determination value of a second survivor path at the first time point, the third determination value being determined by a second sub determination value and a fourth determination value at the second time point; and when a difference between the first determination value and the third determination value is equal to or less than a predetermined value, determining the preferred survivor path at the first time point according to the second and the fourth determination values, or the first and the second sub determination values.