The invention provides a method for laser desorption and ionization, and relates to detection of organic compounds. The invention provides a method for laser desorption and ionization of an organic compound. According to the method, a laser light source is adopted to irradiate the surface of a sample to form a crater; organic compound molecules around the crater are subjected to thermal desorption, such that the organic compound is desorbed into the gas molecules; collision is generated between the desorbed molecules and the high energy electrons or protons generated by the laser, such that the desorbed molecules are subjected to ionization to form the molecular ions with the free radicals form, and the like; a mass analyzer is adopted to analyze the molecular ions with the free radicals form, and the like. With the method, organic solid samples, organic powder samples, inorganic or organic coated organic core particles, organic liquid residues, organic gas sediments, aerosol sediments and the like can be directly analyzed; the matrix-assisted ionization is not required so as to prevent the sample from contaminating, and a wide application range is provided; more ions and fragmentation information can be acquired during the organic compound detection process so as to simplify the identification process of the sample.