Considering the directivity of piezoelectric fiber to Lamb wave, a piezoelectric fiber sensor is fabricated, in which three piezoelectric fibers are arranged in the polymer matrix with 0, 45, and 90 right triangle configuration. Such sensor is similar with traditional strain rosette, thus can be used to detect the income Lame wave direction. The direction information is significant for defect detection. The directional response of piezoelectric fiber under narrowband tone-burst excitation is theoretical deduced, and a numerical estimation method for Lamb wave propagation direction is proposed by defining an error function. Piezoelectric coupling analyses and experimental tests are conducted to validate the directivity property of piezoelectric fiber. Three different piezoelectric fiber configurations, the right triangle (0, 45, 90), Y-type (0, 120, 240), and the equilateral triangle (0, 60, 120) are applied in simulation analyses and experiment tests to validate the accuracy of Lamb wave propagation direction detection. The results show that the piezoelectric fiber sensor is applicable to identify Lamb wave propagation direction and further used to develop efficient defect recognition algorithm without Lamb wave velocity.