Abstract: Considering that high capacity image recorder based on existing invalid block, the method of quickly detection and management invalid block in NandFlash is presented.Based on analysis of written invalid block and non written invalid block, the classified invalid block matching and detection mechanism based on CAM is proposed.On erasing, writing and reading operation of the flash, CAM an SRAM is used to detect and match the invalid block of NandFlash and storage new increased invalid block.When writing high speed image data to the flash, the written data stored into the NandFlash is simultaneously back-up by the external SRAM to prevent image data storage error.The experiment which is based on field programmable gate array (FPGA) indicates the algorithm can identify the invalid blocks in 5 system clock period and storage new increased invalid blocks in 3 system clock periods.The method can quickly identify the consecutive invalid blocks and back-up the written image data.