Background: Chronic kidney disease is common and brings significant health burden. The purpose of this study was to investigate the relationship between physical activity and kidney function. Methods: This was a cross-sectional study set in the Nanjing Community Cardiovascular Risk Survey, using random cluster sampling. Questionnaires were completed, wherever possible, through face-to-face interviews. Data on age, sex, body mass index, weekly physical activity, and kidney function were collected. Physical activity was measured by the metabolic equivalent of task-minutes per week and grouped into “walking,” “moderate,” and “vigorous” according to intensity. Kidney function was measured by the estimated glomerular filtration rate (eGFR, in mL/min/1.73 m2). Regression modeling was used to investigate the proposed relationship with adjustment for other confounding factors. Results: A total of 5824 participants were included, with an average age of 52; 44% were male. The eGFR in average was 76 mL/min/1.73 m2, with 19% ≥ 90, 67% between 60 and 89, and 14% < 60. In average, the total physical activity during a week was 3644 MET-minutes per week. Moderate activity contributed 64% of the total activity, followed by walking (23%) and vigorous activity (13%). Overall, the total activity was weakly associated with eGFR (P = .039). However, in stratified analysis, only walking-related activity was associated with eGFR (P < .0001) after confounding adjustment. Conclusions: Walking is associated with improved kidney function.