A novel cuffless blood pressure (BP) measurement technology is proposed in this paper. Systolic BP (SBP) and diastolic BP (DBP) can be estimated by measuring pulse transit time (PTT) between radial and carotid artery. The pulse signals of artery are measured by split-ring resonator microwave sensors with high sensitivity in a non-contact manner. Instead of measuring resonance frequency deviation, the measurements can be performed by detecting amplitude variation for not only simplified circuits but also increasing sampling rate and sensitivity. In addition, cascading a notch filter can steepen the transition response of sensor to further improves 135 times sensitivity compared to traditional frequency-based method. From experiment results, PTT and BP show the significant negative correlation, and the correlation coefficient is more than -0.79. Based on the relational function of PTT and BP, SBP and DBP can be estimated accurately, and the average error is lower than 8.4%.