A high performance mandarin digit string speaker-independent speech recognition system is given.The acoustic model is based on the Mel Frequency Cepstrum Coefficient and the continuous hidden Markov model (HMM).The multi-candidate frame synchronous search algorithm is adopted in the recognition stage with the MCE algorithm as the training approach.Experiments demonstrate that the correct recognition rate of the system is 94.8% (unknown length) and 96.8% (known length).In order to enhance the flexibility of the system

this paper also conduct research on the maximum a posteriori (MAP) based speaker adaptation and confidence measure based rejection.More than 40% recognition errors can be removed after adaptation and the recognition rate can be improved to 96.9% (unknown length) and 98.7% (known length) when 5% of the correct results are rejected.