We propose full-field functional optical angiography for a live biological specimen based on the absorption intensity fluctuation modulation (AIFM) effect. Because of the difference in absorption between red blood cells (RBCs) and the background tissue under low-coherence light illumination, the moving RBCs, which discontinuously pass though the capillary vessels, generate an AIFM effect. This effect offers high contrast of absorption imaging and sensitivity of low-coherence interference between RBCs and the background tissue. It is used to distinguish the signal of RBCs from that of the background tissue. The averaged and real-time modulation depths are computed to obtain full-field label-free optical angiography and measure blood flow velocity simultaneously. The AIFM method could potentially be applied to study the physiological mechanisms of blood circulation systems of near-transparent live biologic samples.