Abstract: Objective To explore the relationship between peripheral blood monocyte（PBM）subsets and renal injury（RI）in high-salt diet fed spontaneous hypertensive rats（SHR）. Methods Seven-week-old male SHR were randomized to receive 0.5% NaCl diet（low salt,LS group）or 8% NaCl diet（high salt,HS group）for 12 weeks.Blood pressure was measured by tail cuff method. Peripheral blood were collected for flow cytometry analysis at baseline and after 12-week salt intervention. Blood and urine samples were collected for creatinine and microalbumin（MA）determination. At the end of intervention,all rats were anesthetized for blood oxygen level-dependent magnetic resonance imaging（BOLD-MRI）measurements. Picro-sirius red（PSR）staining was performed at time of sacrifice. The relationship between PBM subsets and RI was analyzed. Results Compared with LS group,the urine volume,heart rates and systolic blood pressure（SBP）of HS group were significantly increased while body weight was markedly decreased at the end of intervention（P＜0.05）. Flow cytometry analysis showed that the percentage of CD43⁺⁺monocyte in HS group was apparently increased（8.80±1.69）% vs（1.20±1.08）%while a reduction of CD43⁺monocytes was observed compared with LS group （8.58±1.05）% vs（14.89±1.72）%,both P＜0.05.BOLD-MRI measurements demonstrated that the R2^*（reflect the degree of hypoxia）of renal medulla but not cortex was significantly increased（P＜0.05）. Moreover,PSR staining showed that a severe fibrosis was also found in renal medulla but not cortex of HS group. Meanwhile,renal medulla R2^*was positive correlated with medulla fibrosis. Blood creatinine,the ratio of blood creatinine to urine creatinine,and the urine MA were all significantly increased while urine creatinine was markedly decreased at the end of intervention（P＜0.05）. A positive correlation between the percentage of CD43⁺⁺monocyte and SBP,renal medulla R2^*,renal fibrosis,blood creatinine,the ratio of blood creatinine to urine creatinine,and the MA and a negative correlation between the percentage of CD43⁺⁺monocyte and urine creatinine were also observed. Conclusion The ratio of CD43⁺⁺mononuclear cells in peripheral blood of SHR was increased significantly after 12 weeks of high salt intervention,and this change was related to renal hypoxia,fibrosis and RI.