A memory control circuit unit, a memory storage device and a reference voltage generation method are provided. The method comprises: detecting a first impedance characteristic of a memory controller via a first connection interface of a memory interface and detecting a second impedance characteristic of a volatile memory via a second connection interface of the memory interface; generating an internal reference voltage according to a detection result; and resolving data signal received by the memory interface according to the internal reference voltage. Therefore, an influence on the internal reference voltage owing to the manufacture deviation of impedance element of the memory controller and/or the volatile memory can be reduced.