Brachial-ankle pulse wave velocity (baPWV), as a marker of arterial stiffness, has been demonstrated to be associated with blood pressure (BP) and onset of hypertension. However, little information is available on the associations between baPWV and BP indices [systolic BP (SBP), diastolic BP (DBP), pulse pressure (PP), mean arterial pressure (MAP)] in treated hypertensive patients. We aimed to assess the associations between BP indices and baPWV. In this cross-sectional study, 14,598 hypertensive patients from China Stroke Primary Prevention Trial (CSPPT) at the exit visit of the trial were analyzed. Elevated baPWV was defined as ≥18.3 m/s. Multivariate linear and logistic regression analyses were performed to evaluate the associations of BP indices with baPWV and elevated baPWV. Moreover, the smooth curve fitting (penalized spline method) was conducted. Multivariate linear regression analyses showed that continuous SBP, DBP, PP and MAP were independently and positively associated with baPWV (β = 0.081, 0.084, 0.078 and 0.115, respectively, all P < 0.001). Compared with controlled SBP group (<140 mm Hg), uncontrolled SBP (≥140 mm Hg) was significantly associated with higher baPWV [β = 2.234, 95% confidence interval (CI): 2.137-2.332]. Similarly, compared with controlled DBP group (<90 mm Hg), uncontrolled DBP (≥90 mm Hg) was significantly associated with higher baPWV (β = 1.466, 95%CI: 1.341-1.590). Multiple logistic analyses also showed that SBP, DBP, PP and MAP were significantly and positively associated with elevated baPWV (OR = 1.056, 1.049, 1.052, and 1.075, respectively, all P < 0.001). The fully-adjusted smooth curve fitting presented a linear association between BP indices with baPWV. In conclusion, among treated hypertensive patients, SBP, DBP, PP and MAP levels were independently and positively associated with baPWV and elevated baPWV, suggesting that baPWV might be a way to predict uncontrolled BP.