Fifty-five patients with pSS underwent MRI including DWI to explore whether ADC histogram and texture analyses to evaluate the disease activity of pSS. According to the ESSDAI score, 35 patients were categorized into the low-activity group and 20 into the moderate-high-activity group. ROC analysis showed that the anti-SSB, lip biopsy, MRI morphology, ADC, ADCmean, and entropy values were able to categorize the disease into two groups, particularly the entropy values. The multivariate model, which included anti-SSB, MRI morphology and entropy, had an area under the ROC curve of 0.923. The parotid entropy value distinguished disease activity in patients with pSS.