A vowel-driven connected Mandarin digit recognition system is presented in this paper. Since Mandarin is a monosyllabic language, each syllable has a consonant (may be null) and a vowel. Hence, we develop a segmentation algorithm to segment a connected digit string into the consonant and stable-region parts, where a stable region may contain one or more vowels. The stable-region parts are recognized first. The Mandarin digits, except (1,7) and (6,9), can be recognized just by their vowel parts. While the remaining digit pairs (1,7) and (6,9), which have the same vowel parts, are further distinguished by the special acoustic characteristic of the consonant part. The recognition system is tested in a speaker-dependent mode and under two different cases; known string length and unknown string length. The string error rates of 5.3 % and 7.4 % are achieved in the known-length and unknown-length case respectively.