The invention discloses an STED super-resolution microscope based on first-order Bessel beams and an adjustment method thereof. The STED microscope comprises an excitation light source, a loss light source, an excitation light beam expanding and collimation system, a loss light beam expanding and collimation system, a spiral phase plate, a Bessel beam generation system, a loss light focusing lens, a beam combining system, an object lens, a piezoelectric scanning system, a filter plate, a signal collection system and a single-photon detector. Loss light is the first-order Bessel beams and has scattering-resistant and self-healing characteristics, and great light spot form of the deep position of a sample can be maintained so that resolution of the deep area of the sample can be enhanced. Compared with a method of realizing STED super-resolution microscope deep imaging through adjusting an object lens correction ring, the method is relatively simple in experiment operation without active adjustment. Compared with a method of using a self-adaptive optical system, the experiment device is relatively simple and cheap.