1. A method for speech synthesis based on a large Chinese corpus, comprising: utilizing a prosodic structure prediction model to carry out prosodic structure prediction processing on input text to provide at least two alternative prosodic boundary partitioning solutions, prosodic units located at a same location in the at least two alternative prosodic boundary partitioning solutions being different; acquiring structure probability information about a prosodic unit in the at least two alternative prosodic boundary partitioning solutions according to statistics taken beforehand on data in a Chinese speech corpus, wherein the structure probability information includes a structure probability that the prosodic unit appears at a head or a tail of a prosodic word, a prosodic phrase or an intonation phrase in the Chinese speech corpus; calculating output probabilities of the at least two alternative prosodic boundary partitioning solutions utilizing an output probability calculation function according to the structure probability information; and determining, in the at least two alternative prosodic boundary partitioning solutions, an alternative prosodic boundary partitioning solution of which the output probability is the maximum as a prosodic boundary partitioning solution; and carrying out speech synthesis by acoustic processing to convert the input text into a speech having a pause point and a pause time length according to the determined alternative prosodic boundary partitioning solution.