Abstract: Differential encoding used in conjunction with sequence decoding is a primary method to implement high performance noncoherent demodulation. Though noncoherent decoding based on SCCC with differential encoding is almost similar to coherent demodulation in performance, its high decoding complexity makes its engineering application difficult because of the introduction of modified zero-order Bessel function to estimate the channel transition probability. To solve this problem, two simplified noncoherent MAP decoding algorithms based on SCCC structure are proposed in this paper. These algorithms use an approximate formula of zero-order Bessel function to simplify the branch metrics in log-MAP algorithm of inner decoder. Theoretical analysis and simulation results show that the proposed algorithms can largely reduce the decoding computational complexity and have good performance.