We propose an accurate compact model of nand Flash memory, which is fully compatible with a BSIM-4 model. In sub-30-nm nand Flash, adjacent cells directly affect the channel-edge potential of the selected cell. Due to such direct-channel interference, previous compact models cannot accurately simulate the characteristics of sub-30-nm nand strings. In this letter, we describe the interference as the threshold voltage variation due to adjacent cells and change the threshold voltage equation of the BSIM-4 model. The equation is semitheoretically derived. Using the proposed model, we simulated several behaviors of 27-nm nand Flash strings. The results show more than 90 % accuracy compared with the silicon measurements.