This trial is a randomized, multi-center, parallel-group, efficacy and safety study with a 26-weeks follow- up(after 2-week recruitment). The study aims to: 1)compare the effects of novel flash glucose monitoring system (FGMS) and conventional Self Measurement of Blood Glucose (SMBG); and 2) optimize integrated management for glycaemic control in adult patients with type 1 diabetes who are sub-optimally controlled.

Subjects with Type 1 diabetes who meet criteria will be enrolled at up to eight clinical research sites in China. Subjects will be randomized to either flash glucose monitoring system(Freestyle Libre®;Abbott Diabetes Care,Witney, Oxon,UK) or conventional Self Measurement of Blood Glucose (Bayer®)alone at least three times per day. Primary outcome variable is the difference in HbA1c which will be analyzed in a central laboratory between baseline and the 26weeks follow-up. Secondary outcome variables such as time-in-range, frequency and duration of and hyperglycemic episodes etc. will be assessed at baseline (Week 0 to 2), Week 12-14 and Week 24-26 via professional continuous glucose system (Ipro2®; Medtronic). At the same time, demographic factors, clinical data, patient reported outcome (PROs) will be collected. Assessment of Adverse Events will occur via self-reporting at each visit and/or phone call. All patients will receive same ordinary diabetes education.

Inclusion Criteria:

1. Aged 18 years and older;
2. Diagnosed with type 1 diabetes with the criteria established by WHO in 1999,with duration more than 1 year;
3. Glycosylated Hemoglobin A1c concentration between 7% and 10%;
4. Self-monitor of blood glucose levels on a regular basis for 2 months previous( at least 3 times per day) and have willing to insist for at least 6 months
5. Using CSII or MDI for at least 3 months, stable diabetes medication regimen for 3 months prior to study entry(change in insulin ≦20%).
6. Willing to wear CGM;
7. Able to speak, read, and write Chinese

Exclusion Criteria:

1. Having used CGM 3 months prior to study entry;
2. Had severe diabetic complications such as PDR in diabetic retinopathy and ESRD of diabetic nephropathy, assessed by investigators;
3. Receiving oral steroid therapy for any disorders and continuous use of paracetamol.
4. Had known allergy to medical-grade adhesives or CGM and its affiliated components;
5. Being pregnant or planning pregnancy (as demonstrated by a positive test at study entry);
6. Recent severe diseases like myocardial infarction,stroke,psychiatric diseases(historical/recent),malignant tumor, kidney disease(defined as eGFR<45), dermatosis, decided by investigator.
7. Current participation in another investigational study (must have completed any previous studies at least 30 days prior to being enrolled in this study);
8. Currently abusing illicit drugs, alcohol, or prescription drugs;
9. Any condition that could impact reliability of the HbA1C measurement,（e.g.hemoglobinopathy, hemolytic anemia, chronic liver disease),decided by investigator.