Abstract: Objective To observe early moming hyperglycaemia “dawn phenomenom” in type 2 diabetes mellitus with continuous glucose monitoring system and assessment of curative effect by Metformin Hydrochloride. Methods fifty-six type 2 diabetes patients with dawn phenomenom was measured by continuous glucose monitoring system before Metformins Hydrochloride were taken,assessment of curative effect before and after Metformin therapy. Results The dawn phenomenom were observed in patients by CGMS. Metformin Hydrochloride,0.5-0.85g,QN were given and the dawn phenomenon were improved significantly. The attainment rate of the blood glucose were 85.7%.verage glycemic values、The mean amplitude of glycemic fluctuation、The percentage of TBG ≥8.0 mmol/L were reduced,there were significant diferences(P<0．05)．The percentage of TBG≤ 3.9mmol／L were no significant diferences after treatmate(P>O．05)．Conclusions Metformin Hydrochloride can effectively improve the “dawn phenomenom”in some type 2 diabetes patients.