A data accessing method and a system for use with the same are provided. A processing unit reads a command from a memory unit and decodes the command. Then, the processing unit determines if the command requires pre-fetching of data that are not stored in a cache or a buffer unit; if yes, the processing unit sends a fetching request to the memory unit according to addresses of data to be fetched and pre-fetched. Moreover, the processing unit reads the data to be fetched from the memory unit and stores the data to be pre-fetched in the buffer unit. Thereby, the above method and system can achieve data pre-fetching accurately.