Method and apparatus of using a system memory for 3D comb filtering for PCTV application are provided. Firstly, the data reading/writing in a logic address may be controlled, and mapping the logic address to a physical address in the system memory, and actually reading/writing data in the physical address. A RSM and a WSM may be used to control reading/writing data in the logic address respectively, wherein the WSM switching among its idle status, request status, and processing status, and the RSM switches among its idle status, request status and waiting status. An address mapping table may be used to record the logic address and corresponding physical address. Upon obtaining the physical address via the address mapping table, actually reading/writing data in the physical address. Method and apparatus for adaptively controlling of 3D comb filter on/off depending on the status of the video decoder and on-chip memory. The present invention is advantageous for using system memory for 3D comb filtering over two or more frames.