The invention provides a non-invasive blood pressure detecting system and method based on finger artery waves. The detecting system comprises two photocapacitance pulse wave sensors, a filtering and amplifying circuit, a microprocessor master control circuit, a battery module, a mobile communication module and a cloud platform. The detecting method includes the steps that firstly, photocapacitance pulse wave signals of two points in front of and behind the same finger artery are acquired at the same time, after being filtered and amplified, the two paths of photocapacitance pulse wave signals are subjected to AD conversion, corresponding feature points are subjected to position marking, the waveform feature point time difference between the two paths of waves is calculated, pulse wave conduction time is obtained, and a linear equation is established according to the direct proportion relation between blood pressure and the pulse wave conduction time; finally, the obtained pulse wave conduction time and blood pressure data obtained through a sphygmomanometer are substituted into the linear equation, individual undetermined parameters are calibrated, new pulse wave conduction time is substituted into the linear equation obtained after the parameters are determined, and the blood pressure of a testee is obtained through calculation. The non-invasive blood pressure detecting system is light, small and ingenious in design, no traditional cuff is needed, and the testing result is precise.