Abstract: 1-Bit Compressive Sensing (CS) is an important branch of standard CS. The existing 1-Bit CS algorithm-Binary Iterative Hard Thresholding (BIHT) can perfectly recovery signals with high precision and consistency, which requires exact sparsity level in the recovery phase. Considering this problem, a new Sparsity Adaptive Binary Iterative Hard Thresholding (SABIHT) algorithm without prior information of the sparsity is proposed by modifying the BIHT algorithm. By using the adaptive process of automatically adjusting the hard threshold parameters and test conditions to estimate the sparsity, the proposed algorithm realizes accurate reconstruction and estimates the true supporting set of approximated signal. The analytical theory and simulation results show that the SABIHT algorithm recovers effectively the signals without prior information of signal sparsity and the reconstruction performance is similar to the BIHT algorithm.