1. A controllable prosody re-estimation system implemented in a computer system having at least a processing device and an input device, comprising: a controllable prosody parameter interface responding to the input device for loading a controllable parameter set; and a speech/text to speech (STS/TTS) core engine, said core engine including at least a prosody prediction/estimation module, a prosody re-estimation module and a speech synthesis module, at least one of which is executed by said processing device, wherein said prosody prediction/estimation module predicts or estimates prosody information according to the input text/speech, and transmits the predicted or estimated prosody information to said prosody re-estimation module; said prosody re-estimation module produces new prosody information according to said input controllable parameter set and predicted/estimated prosody information, after which said prosody re-estimation module transmits said new prosody information to said speech synthesis module to generate synthesized speech, wherein said system further constructs a prosody re-estimation model, and said prosody re-estimation module uses said prosody re-estimation model to re-estimate said prosody information so as to produce said new prosody information, wherein said prosody re-estimation model is expressed in the following form: 
 X rst =Δμ+[μ src +( X src −μ src )ρ×γ] wherein X src is prosody information generated by a source speech, X rst is the new prosody information, μ src is the mean of prosody of a source corpus, and (Δμ, ρ, γ) are three controllable parameters.