An adaptive detection scheme is proposed on the very fast detection algorithm for Space-time block code in IEEE 802.11ac. At first, QR decomposition is applied to the channel matrix for getting an upper triangular matrix and has been achieved the required number of candidate constellation points around the maximum likelihood (ML) points without considering all possible candidate constellation set. Finally, the ratio of the diagonal elements of upper triangular matrix adaptively determines the number of candidates to reduce the further complexity of the searching process. However, the error performance of the proposed scheme is not very close to the ML detection, but the computational complexity can be reduced by 83% as compared to the very fast detection algorithm at a bit error rate (BER) 10 -- 4.