A look-up table which is required during looking up table for data transferring and a method for looking up table are provided. The method reduces the size of the look-up table used in the method for looking up table by simplifying the calculations. A reasonable error range is obtained for the required look-up table by adjusting appropriate modifiers. The method can be applied in the method for looking up table similar to the Q ⁡ ( x ) = x B A calculation in the digital signal coder/decoder (CODEC), where both A and B are integers, and the calculation is more efficient if B/A is close to 1 or smaller than 1.