Objective To investigate doctors'knowledge and differences in islet function assessment methods in China.Methods This is a cross-sectional study that conducted by online questionnaire survey.Demographic data,examination items,blood collection point of OGTT,detection method,kit type and follow-up frequency were collected and compared among doctors in different regions,different levels of hospitals,different specialties and different titles.Results 79.2%and 85.1%of physicians believed that the levels of insulin and C-peptide should be measured at the same time to assess islet function in patients with newly diagnosed and follow-up diabetes mellitus patients.Endocrinologists preferred to access insulin and C-peptide at the same time(P<0.05).56.0%of physicians chose bread meal test for T1DM patients and 54.7%for T2DM patients.Compared with non-specialists,endocrinologists preferred to commit bread meal test to T1DM patients(61.4%vs 41.0%,P<0.05).In addition,for the islet function assessment of new-onset diabetes patients,7.6%of physicians chose the six-point method(0,30,60,90,120,180 min),27.3%selected the five-point method I(0,30,60,120,180 min),8.5%selected the five-point method II(0,30,60,90,120 min),9.8%selected the four-point method I(0,30,60,120 min),10.3%selected the four-point method II(0,60,120,180 min),13.8%chose the three-point method(0,60,120 min)and 13.4%chose the two-point method(0,120 min).At the time of follow-up assessment,the above selection rates were 5.3%,20.4%,6.4%,6.6%,9.4%,15.8%and 24.1%,respectively.In terms of the frequency of assessment,39.2%of doctors assessed islet function once a year and 24.7%once every six months.Specialists preferred to assess islet function once a year,and physicians with senior titles chose to assess islet function more variably.Conclusion At present,there are still great differences in assessment methods of islet function in China.It is of great significance for the clinical diagnosis and treatment of diabetes to understand the differences in the selection of islet function assessment methods among doctors in different regions,specialties and job titles.