Objective: To investigate the effect of nitric oxide (NO) and nitric oxide synthase (NOS) on cerebrovascular reactivity (CVR) in patients with cerebral infarction. Methods: In the prospective case-control study, 193 patients with cerebral infarction in internal artery system within 2 weeks were used as cerebral infarction group, and 103 normal healthy subjects were used as control group. Griess diazotization assay and enzyme-labelled immunosorbent assay were used for measuring the concenration of NO product and NOS activity in both groups; the breath-holding index (BHI) was obtained by transcranial Doppler combined with breath-holding test to evaluate CVR. Results: BHIs in the cerebral infarction and control groups were 1.0 ± 0.4 and 1.4 ± 0.5, respectively; the median concentration of NO product was 6.04 (3.83 - 11.49) μmol/L and 6.89 (4.64 - 12.43) μmol/L, respectively; NOS activity was 3.0 ± 1.5 U/mL and 3.2 ± 1.5 U/mL, respectively. BHI and the cocentration of NO production in the cerebral infartion group were lower than those in the control group (all P < 0.05 ). BHI showed positive correlation with NO production (r = 0.39, P = 0.000), and there was no correlation with NOS. There was no NOS activity difference between the two groups (P = 0.517). Conclusions: There were certain correlations between the decrease of CVR in patients with cerebral infarction and the reduction of NO content, however, the relations between CVR and NOS activity remained uncertain. NO may be one of the factors in regulating CVR.