A decoding method, a memory controlling circuit unit, and a memory storage device are provided. The method includes: when first data is read from a first upper physical programming unit of a first physical programming unit group by using a second voltage selected from a first read voltage group, and a first error bit count of the first data is not greater than a first error bit count threshold, recording the second voltage; when a second data is read from a first lower physical programming unit of a second physical programming unit group by using a fourth voltage selected from a second read voltage group, and a second error bit count of the second data is not greater than a second error bit count threshold, recording the fourth voltage; generating a lookup table according to the second voltage and the fourth voltage; and performing a decoding operation according to the lookup table.