The invention relates to a laser system, a working method and a projection system. The laser system comprises a laser source, a collimation system and a self-focusing system, wherein the laser source transmits a monochromatic laser beam; the collimation system collimates the laser beam transmitted by the laser source; and the self-focusing system focuses the laser beam which is emergent from the collimation system. The invention adopts the laser source as the light source of the projection system, and the laser source has long service life, small volume, low power consumption, wide colour gamut, high brightness, environmental protection, easy mass production and low cost. In addition, the self-focusing system is adopted in the laser system to focus the laser beam, the focusing capability is stronger, light spots are smaller, energy is more concentrated, and the laser efficiency is higher.