1. A Maximum A Posteriori (MAP) algorithm-based Turbo decoding method, an information symbol being sequentially divided into a plurality of sub-blocks, each sub-block comprising a plurality of sliding windows, the method comprising: iteratively estimating an information symbol by using an MAP algorithm, acquiring α and β boundary values for each sliding window and each sub-block by means of window boundary value inheritance and block boundary value inheritance, and recursively calculating posterior probability Log Likelihood Ratio (LLR) values of a whole window and a whole block according to the α and β boundary values; and performing decoding decision according to the LLR values, wherein acquiring an α boundary value for a sliding window by means of window boundary value inheritance and block boundary value inheritance comprises: taking an α boundary value, acquired in a previous iteration, as an initial value of α in a present iteration, forwardly reading input data of the whole window of the sliding windows, and calculating an α value of the whole window; and acquiring a β boundary value for a sliding window by means of window boundary value inheritance and block boundary value inheritance comprises: taking a β boundary value, acquired in the previous iteration, as an initial value of β in the present iteration, reversely reading the input data of the whole window of the sliding windows, and calculating a β value of the whole window, and wherein in order to calculate β values, write and read addresses of a RAM for storing the input data range from 0 to K−1 and range from K−1 to 0 respectively, where K is a data length of a window.