A method for calculating blood pressure based on pulse return wave transmission time, and a blood pressure monitor have been provided. The method includes the following steps: S1: collecting and storing pulse waveform data at a fingertip; S2: processing said pulse waveform data to obtain a heart rate and parameters of a plurality of pulse periods, detecting time axis coordinates of a primary wave starting point SPL1 of a pulse wave and a growth point SPL2 of a return wave in each of said pulse periods, and calculating a corresponding pulse return wave transmission time RWTT: RWTT=SPL2−SPL1; S3: calculating the pulse return wave transmission time RWTT in each of said pulse periods to form a RWTT array; and S4: calculating systolic and diastolic pressures based on said RWTT array and the heart rate.