suppose $l$ is a link with n components and the rank of $kh(l;z/2)$ is $2^n$, we show that $l$ can be obtained by disjoint unions and connected sums of hopf links and unknots. this result gives a positive answer to a question asked by batson-seed, and generalizes the unlink detection theorem of khovanov homology by hedden-ni and batson-seed. the proof relies on a new excision formula for the singular instanton floer homology introduced by kronheimer and mrowka. this is joint work with yi xie.