Absolute blood flow velocity and orientation are measured by a dual-mode imaging technology using photoacoustic microscopy and optical coherence tomography (PA/OCT). The blood flow velocity perpendicular to the direction of the probe beam is measured by photoacoustic correlation spectroscopy. The blood flow velocity parallel to the direction of the probe beam is measured by the Doppler OCT. Then the absolute velocity and orientation of blood flow are obtained. For the same fluid sample with different tilt angles, the standard deviation of the absolute blood flow velocity which is 1 mm·s -1 measured by PA/OCT is 0.02 mm·s -1 and the correlation coefficient between the blood flow orientation measured by PA/OCT and the actual flow orientation is 0.997. The experimental results show that the PA/OCT is suitable for measuring absolute blood flow velocity and orientation.