Computer system and direct RAM access transmission method

The invention relates a computer system and a direct memory access and transformation method which includes that receive direct memory access and data transformation request; according to it, configure descriptor linked list of the source data describing source data and descriptor linked list of the destination data describing destination data; receive direct memory access request; judge whether the rest length of the source data block is zero, if it's true, read the descriptor linked list of the source data from descriptor linked list of the source data; judge whether the rest length of the destination data block is zero, if it's true, read the descriptor linked list of the destination data from descriptor linked list of the destination data; if the rest length of the source data block and the destination data block is greater than zero, transmit data according to transmission parameters. The computer system and direct memory access method that the invention describes needn't to segment continuous data block in physical address, can decrease computation of microprocessor of computer system, and can promote the performance of computer system.