The invention provides a continuously tunable single-frequency Ti sapphire laser device. The continuously tunable single-frequency Ti sapphire laser device comprises a pump source (3), a Ti sapphire crystal (2), a laser resonant cavity, an isolator, a double-refraction filter (4), an etalon (5) and piezoelectric ceramic (14), wherein a nonlinear crystal (1) is inserted between a third flat concave mirror (11) and a fourth flat concave mirror (12) forming the laser resonant cavity, the nonlinear crystal (1) is an optical crystal machined to be provided with two unparallel light through surfaces or an optical crystal placed in a light path at a Brewster angle; moreover, the nonlinear crystal (1) is used for realizing generation of second harmonics of the base-frequency light of the laser device in a mode of critical phase matching or noncritical phase matching. According to the continuously tunable single-frequency Ti sapphire laser device provided by the invention, the nonlinear loss stressed by the main oscillation mode of the base-frequency light is one half of a non-oscillation mode, thus the oscillation starting of the non-oscillation mode of the base-frequency light is effectively suppressed, and the laser device realizes continuously tunable property for the frequency in a valid gain bandwidth. The laser device is compact in structure and convenient to operate.