The invention relates to an adjustable picosecond laser. The adjustable picosecond laser is formed through the connection of all-polarization maintaining optical fiber devices; one end of the picosecond laser is a saturable absorption device, and then a gain optical fiber, a wavelength division multiplexer, a beam splitter, an optical switch, a plurality of delay optical fibers and optical fiber gratings correspondingly connected with the delay optical fibers one by one are orderly connected behind the saturable adsorption device; the other input port of the wavelength division multiplexer is connected with a pumping source, the other two ports of the beam splitter are respectively used as an oscillator output end and a monitoring end. An optical fiber link designed with the all polarization maintaining structure can resist the environment interference, and guarantee the long-term stabilization of the output pulse; a plurality of pulse widths, working wavelengths and repetition frequency required by the application can be previously set; by use of the optical switch, the adjustable picoseconds laser can be flexibly switched in multiple laser output parameters, so that application requirements can be met; and compared with the semiconductor picosecond laser in electric pulse modulation, the average power output by the adjustable picosecond laser is high, and adjustable picoseconds laser is more suitable to be a seed source for subsequent laser amplification.