Considering that the receiver was not only affected by the non-Gaussian noise but also affected by its internal and external environment of Gaussian noise, a mixed model composed by non-Gaussian distribution plus Gaussian distribution was proposed. A blind detection algorithm based on Markov Chain Monte Carlo method was designed according to the properties of the mixed model. The blind detection algorithm could estimate the channel fading coefficient, parameters of noise model and could detect signal element. Detect signals based on Bayesian hierarchical model was using Gibbs sample and M-H sample for parameter updating. The algorithm has a high iterative efficiency and precision. Results show that the proposed blind detection algorithm performs as well as the optimal detection algorithm and has important realistic significance in super low-freguency signal reception.