A memory power supply control circuit includes a number of memory slots, a platform controller hub (PCH), a first synchronous rectification driver, a number of second synchronous rectification drivers, and a complex programmable logic device (CPLD). The PCH is connected to the memory slots. The first synchronous rectification driver maintains a working state at all time. The CPLD is connected between the PCH and the second synchronous rectification drivers. The CPLD receives information from the PCH to determine a number of used memory slots, and controls the working states of the second synchronous rectification drivers according to the number of used memory slots.