Objective To study the global cognitive function and executive function of non-dementia type 2 diabetes patients， and explore the optimal blood glucose control level of type 2 diabetes patients from the perspective of cognitive function.Methods From July 2018 to July 2019， 309 patients with type 2 diabetes mellitus (T2DM group) and 132 patients without diabetes control group (control group) were enrolled in the Department of Neurology of The Third People's Hospital of Chengdu. General clinical data were collected. The differences of MMSE， MOCA， STT and SCWT between the two groups were compared. T2DM group was divided into 3 subgroups according to HbA1c level， namely HbA1c < 7% group， 7%≤HbA1c < 8% group and HbA1c≥8% group. MMSE， MOCA， STT and SCWT of the 3 subgroups were compared with the control group.Results There was no statistical difference in general clinical data between T2DM group and control group. The MOCA score of T2DM group was lower than that of the control group. The STT-A time， STT-B time， STT time difference， SCWT-A time， SCWT-B time and SCWT-C time were longer than that of control group， and SCWT-C correct was lower than that of control group. The level of HbA1c in T2DM group was correlated with the global cognitive function and executive function. No difference on global cognitive function or executive function was observed when HbA1c<7% compared with control group. When HbA1c≥7%， the MOCA score and some executive function indices were lower than that of control group. When HbA1c≥8%， more executive function indexes were lower than those in the control group and HbA1c<7% group.ConclusionPatients with type 2 diabetes have the decline of global cognitive function and executive function even in non-dementia stage， which is related to the level of blood glucose control. From the perspective of cognitive function， it is still recommended that HbA1c should be controlled between 6%~7% to delay cognitive impairment.