In this article, we studied how meditation affects the characteristics of the cardiovascular system, mainly based on blood pressure waveforms (BPW). Four parameters derived from BPW include the rising slope (h(1)/t(1)), normalized height of T wave (h(3)/h(1)), normalized height of V(3) valley (h(4)/h(1)) and normalized height of D wave (h(5)/h(1)), where t(1) and h(i), i = 1, ... ,5 are quantitative features of the BPW waveform pattern. A larger value of h(1)/t(1) reflects better heart ejection ability and aorta compliance. A larger value of h(3)/h(1) may infer an arterial system with good elasticity. The decrease (increase) of h(4)/h(1) parameter indicates the decrease (increase) of peripheral resistance of vessels. A larger value of h(5)/h(1) indicates better artery elasticity and aortic valve function. In comparison with the control group, Zen-meditation practitioners have more after-meditation h(1)/t(1), h(3)/h(1) and h(5)/h(1) increase, with more h(4)/h(1) decrease, with statistical significance (P < 0.05). The observation allows us to infer that Zen meditation may effectively improve relevant characteristics of the cardiovascular system.