A decoding method for unary/kth order exponential Golomb (UEGk) codes is provided. The first step is a receiving step: receiving N bits from an input stream and updating a bit count. If the N bits are all one, the receiving step is re-performed. If the N bits includes zero, a searching step is performed to find a first value based on the bit count. Subsequently, according to the bit count and a threshold value, a remaining bit number M is calculated. A second value is generated based on M remaining bits received from the input stream. Then, the first value and the second value are added, so as to generate an index.