A memory access system for accessing a basic input output system (BIOS) program is provided. The memory access system includes a flash memory, a CPU, a peripheral component interconnect (PCI) slave, an address converter and a flash memory controller. The flash memory stores a number of BIOS data of the BIOS program, and each BIOS data corresponds to a default BIOS address and is allocated in a flash memory type BIOS address. The CPU delivers a BIOS access instruction. The BIOS access instruction corresponds to a default target address of the default BIOS addresses. After the PCI slave interprets the BIOS access instruction, the address converter converts the default target address into a flash memory type target address, which is one of the flash memory type BIOS address. The flash memory controller accesses the BIOS data allocated at the flash memory type target address accordingly.