| Outcome Measures: |
Primary: the mean change in glucose area under curve (AUC) from baseline., Compared with placebo, the mean change in glucose AUC from baseline at D28., 28 days | Secondary: the fasting plasma glucose from baseline, Compared with placebo, the fasting plasma glucose from baseline at D7，D14，D21 and D28., 7, 14, 21, 28 days|the changes of MMTT (mixed-meal tolerance test) results from baseline, Compared with placebo, the changes of MMTT (mixed-meal tolerance test) results from baseline at D28, 28 days|the mean changes of average 7-points blood glucose profiles from baseline, Compared with placebo, the mean changes of average 7-points blood glucose profiles from baseline at D7，D14，D21 and D28., 7, 14, 21, 28 days|the mean changes of average 14-points blood glucose profiles from baseline, Compared with placebo, the mean changes of average 14-points blood glucose profiles from baseline at D7，D14，D21 and D28., 7, 14, 21, 28 days|the mean changes of post-prandial blood glucose from baseline, Compared with placebo, the mean changes of post-prandial blood glucose from baseline at D7，D14，D21 and D28., 7, 14, 21, 28 days | Other: genetic: TCF7L2 ( Transcription factor 7-like 2) rs7903146 and GCKR (glucokinase regulatory protein) rs780094 ), The genetic（TCF7L2 rs7903146 and GCKR rs780094）effects on response of SY-004 in T2DM patients., 28 days|the changes of GA (Glycated albumin) from baseline, Compared with placebo, the changes of GA (Glycated albumin) from baseline at D28., 28 days
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