Lithium niobate has been widely used in the fabrication of high-performance electro-optic waveguide modulators and switches in the past decades because of its wide transparent window, mature waveguide fabrication technologies, and remarkable electro-optic effect. In recent years, with the advent of high-quality commercialized thin film lithium niobate, a variety of high-performance thin film lithium niobate optical waveguide devices have been demonstrated experimentally, and the performance of these devices has far exceeded their counterpart fabricated with conventional bulk lithium niobite wafer. In this paper, the progress of optical waveguides, couplers, electro-optical modulators, and tunable filters on thin-film lithium niobate platforms in recent years are reviewed, and the challenges faced by thin-film lithium niobate waveguide devices are briefly discussed.