Objective To assess the myocardial blood flow and reserve function by rest and stress 13 N-NH3 PET myocardial perfusion imaging ( MPI) , and evaluate the diagnostic value of PET and risk fac-tors of non-obstructive coronary microvascular disease ( CMVD) type 1. Methods A total of 56 patients (28 males, 28 females;age:(52.0±7.6) years) with clinical suspected CMVD type 1 from April 2017 to December 2018 were prospectively enrolled. The coronary CT angiography, coronary angiography and other clinical data were recorded. All patients underwent one-day rest and stress 13 N-NH3 PET MPI. Images were analyzed and the absolute myocardial blood flow ( MBF) and coronary flow reserve ( CFR) were obtained. Patients were divided into CMVD type 1 ( CMVD) group and non-CMVD group. The differences between 2 groups were analyzed by two-sample t test and logistic regression. Results Among 56 patients, 20 patients were diagnosed as CMVD type 1, and 36 patients were excluded as non-CMVD group. The proportion of smoking and diabetes in the CMVD group was significantly higher than that in the non-CMVD group (χ2 val-ues:9.433 and 4.114, both P<0.05). The stress MBF ((2.37±0.61) vs (3.83±1.25) ml·min-1·g-1;t=-4.807, P<0.001) and CFR (2.67±0.60 vs 3.81±0.96;t=-4.751, P<0.001) were lower in smokers than those in non-smokers, and the stress MBF was lower in diabetes patients than that in non-diabetes patients ((2.63±0.98) vs (3.62±1.28) ml·min-1·g-1;t=-2.758, P=0.008). Smoking might be the risk factor for lower stress MBF (odd ratio (OR)=0.310, 95％ CI:0.114-0.880) and lower CFR (OR=0.278, 95％ CI:0. 080-0.894), and diabetes might be the risk factor for lower stress MBF (OR=0.254, 95％ CI:0.073-0. 887) . Conclusions PET MPI can be used for the diagnosis of CMVD type 1. Smoking and diabetes are likely to be associated with the onset of CMVD type 1.