Objective:To investigate the effects of insulin glargine administration by jet injection versus conventional insulin pen on glucose profile using professional mode flash glucose monitoring(FGM) system in type 2 diabetic patients with poor glucose control.Methods:In this randomized, controlled, crossover study, 40 patients with T2DM who treated with insulin glargine were enrolled. The patients were randomly divided into group A(jet injector-conventional pen, n=20) and group B(conventional pen-jet injector, n=20). Each patient wore FreeStyle Libre sensor from day 4 to day 17. The specialist nurse instructed patients how to master the injection techniques. Professional FGM system was applied to assess glucose profile. Results:The fasting blood glucose(FBG) of the enrolled patients was(9.37±1.84) mmol/L. In contrast to conventional insulin pen, treatment with the jet injector significantly decreased the 24h MBG [(9.06±2.13 vs 9.98±2.67) mmol/L, P=0.001], MaxBG [(16.69±3.01 vs 17.95±3.48) mmol/L, P=0.001], AUC>10 mmol/L [95.93(21.12, 129.02) vs 142.66( 27.88, 198.46), P=0.002], TAR(31.10±21.89 vs 39.49±25.93, P=0.003), MAGE and SDBG. It was observed that patients using jet injector had significant increased TIR(65.94±20.47 vs 58.32±25.00, P=0.001). There were no difference in the risk of hypoglycaemia between two groups. Conclusion:Insulin jet injector was more effective than the insulin pen on glycaemic control and glucose fluctuation without increasing the risk of hypoglycemia in type 2 diabetic patients with uncontrolled glycemia.