Many aquatic and aerial animals have evolved highly sensitive flow receptors to help them survive in challenging environments. The biological flow receptors, such as filiform hairs, lateral lines, and seal whiskers, are elegantly designed with interesting biomechanical processing principles for extreme sensitivity, exhibiting obvious morphological intelligence. For instance, superficial neuromasts on the surface of fish body have an elongated cupula to enhance flow detection with a magnified drag. The flow-induced mechanical information is transferred to arrayed hair bundles in the neuromasts, which show spontaneous oscillation and mechanical coupling effects for a high mechanical sensitivity. In this review, the biomechanical principles of morphological intelligence in biological flow field receptors are discussed, with an emphasis on the functions of stimulus enhancement, noise reduction, and nonlinear oscillation. In addition, the recent achievements in flow sensors with morphological intelligence are summarized in this article. Though there is still a big gap in principle discovery and practical application of morphological intelligence in engineered sensors, it can be anticipated that the field of intelligent flow sensing will be significantly promoted by the establishment of morphological intelligence models.