Objective： To investigate the value of functional magnetic resonance imaging (MRI) in evaluating the status of kidney grafts after renal transplantation. Methods： A total of 52 patients with stable renal function who underwent renal transplantation in the First Affiliated Hospital of Nanjing Medical University from January 2018 to December 2019 were selected as the study objects. The clearance rate of 99mTc DTPA was used as the reference glomerular filtration rate (rGFR), and the GFR of kidney grafts was estimated by dynamic contrast-enhanced （DCE）-MRI. The estimated DCE-MRI results were compared with rGFR using bias, accuracy, correlation, consistency and diagnostic analysis. Four groups of rat models were established: syngeneic graft group (SYN), renal ischemiareperfusion injury group (IRI), T cell mediated rejection group (TCMR) and antibody mediated rejection group (ABMR). The apparent diffusion coefficient (ADC) was measured by DWI sequence scanning on the 7th day after operation. After the examination, all rats were sacrificed immediately, and the transplanted kidney tissues were harvested for histological examination. Results： There was a significant positive correlation between the estimated GFR by DCE-MRI and rGFR (r=0.71, P<0.01). The consistency analysis showed that the bias was -3.544 mL/(min·1.73 m2), the accuracy was 15.33 mL/(min·1.73 m2), and the 95% confidence interval was 60.07 mL/(min·1.73 m2). DCE-MRI had an area under the curve of 0.91 with sensitivity of 79.17% and specificity of 82.14% in the diagnosis of patients with CKD stage 3 and above ［GFR<60 mL/(min·1.73 m2)］. Further animal experiments showed that there was no statistical difference in renal medulla ADC values between the four groups. In the meantime, renal cortex ADC values in SYN and IRI exhibit no significant difference. It′s worth noting that the cortical ADC values in TCMR group and ABMR group were significantly lower than those in SYN group (P<0.05), while there was no significant difference between TCMR group and ABMR group. In addition, the acute rejection group (TCMR group and ABMR group) had significantly lower renal cortical and medullary ADC values than those in the SYN group and IRI group (both P<0.05). Conclusion： Functional MRI could effectively and safely evaluate the renal function of patients after renal transplantation, with high sensitivity and specificity. In animal experiments, acute rejection after kidney transplantation can be well diagnosed by functional MRI.