Objective: To explore the effect of cardiorespiratory fitness (CRF) on cardiometabolic health and physical activity among obese adolescents, in order to provide a scientific basis for health promotion of obese adolescents. Methods: From July to August 2021 and 2022, 140 obese adolescents aged 10-17 were recruited in a residential weight loss camp. Sedentary behavior (SB), low intensity physical activity (LPA), total physical activity (TPA) and moderate to vigorous physical activity (MVPA) were measured by ActiGraph GT3X+ triaxial motion accelerometer, and CRF levels were measured by 20 meter shuttle run test. Cardiometabolic risk Z score (CMR- Z ) was constructed by measuring the cardiometabolic health indicators of obese adolescents, including waist circumference (WC), sagittal abdominal diameter (SAD), systolic blood pressure (SBP), diastolic blood pressure (DBP), average blood pressure (ABP), fasting insulin (FINs), fasting plasma glucose (FPG), total cholesterol (TC), and high density lipoprotein cholesterol (HDL-C). The mediating effect analysis was conducted by using the SPSS Process plug in compiled. Results: Cardiovascular health indicators WC, SAD, SBP, DBP, ABP, FINs, FPG, TC, HDL-C and CMR-Z were (93.21± 11.51 )cm, (21.77±2.71)cm, (111.24±11.86)mmHg, (66.08±9.03)mmHg and (88.66±8.97)mmHg, (8.98±6.42)μU/mL, ( 4.42 ±0.62)mmol/L, (4.43±0.97)mmol/L, (1.29±0.28)mmol/L, -0.43(-1.83,1.78)min, respectively. In the daily activity behavior indicators, the duration of SB, LPA, MVPA and TPA were (345.16±78.47, 267.35±62.65, 64.77±39.52, 677.30±57.63)min, respectively. SB, LPA and MVPA accounted for 50.96%, 39.47% and 9.56%, respectively. The indicator VO 2max of CRF was (37.95±4.96)mL/(kg min). Mediation analysis showed that CRF played a fully mediating role between LPA and waist to height ratio (WHtR), accounting for 44.2%. It exhibited a suppressing effect between LPA and ABP accounting for 31.5%, with a suppressing effect between MVPA and SAD accounting for 43.2% and a suppressing effect between MVPA and CMR- Z accounting for 96.0%. Conclusions CRF may be an important factor in the relationship between physical activity and cardiometabolic health of obese adolescents. Improving CRF level may be conducive to promoting cardiometabolic health of obese adolescents.