In this paper, a blind signal-to-jamming-plus-noise ratio (SJNR) estimation under typical tone-jamming is proposed in a Rayleigh fading channel. Based on the differences among communication signal, jamming, and noise in cyclostationarity, the proposed algorithm obtained SJNR values by using different parts of the cyclic autocorrelation matrix of received signals and applying the minimum square error (MSE) method to estimate the communication signal power and jamming-plus-noise power, respectively. Through deriving the Cramer-Rao lower bound (CRLB) for the SJNR estimation, the normalized MSE performance is examined. Simulation results show that the proposed estimation performs better than the subspace-based eigenvalue decomposition estimation on a normalized estimation bias, and its normalized MSE performance is also closer to CRLB. absence of jamming. These provide the needed channel quality information for many adaptive technologies, such as power control [9,10], transmission rate adaption [11], handoff [12], and channel allocation control [13].Signal-to-noise ratio and SINR estimations are generally divided into two categories: non-blind estimation method, also known as data-aided method, which sends periodic training sequence or pilot frequency sequence, and thus to estimate the SNR and SINR. Blind estimation method, that is, non-data-aided method does not send the training sequence or secondary data but estimate them only by characteristics of communication signals. The complexity of non-blind estimation is lower with better real-time, but it certainly occupies part of the effective bandwidth and reduce transmission efficiency while sending training sequence. Blind estimation method does not take up communication spectrum, its transmission efficiency is higher, but usually the estimation complexity is also higher, and it requires longer data sequence, the real-time is poor, and the accuracy is slightly worse. Non-blind estimation is the main application of the existing communication system, but to improve the transmission efficiency of the system, the research on blind estimation algorithm is more active. The existing SNR estimations mainly include maximum likelihood (ML) criterionbased estimations [14,15] and estimations based on second-order or higher-order statistics [16,17]; the existing SINR estimations mainly include moment-based estimations [18-20] and subspacebased (SB) eigenvalue decomposition estimations [21,22]. However, the fact that jamming may exist is not taken into account in most existing SNR estimations that only consider the impact that white Gaussian noise (WGN) has. Therefore, it may be difficult to provide accurate channel quality information for system adaption in the presence of jamming. Meanwhile, the existing SINR estimations, which are mainly aimed at the co-channel interference and adjacent channel interference (self-interference) produced by wireless cell systems (like code division multiple address (CDMA) and time division multiple address (TDMA)) and easily processed by equating...