The embodiment of the invention discloses a method and a system for processing oil field wastes. The method for processing the oil field wastes comprises the following steps: conveying initial materials to a heating cavity, and heating the heating cavity by using high-temperature flue gas, so as to obtain mixed steam and solid residues; carrying out condensation and separation on the mixed steam, so as to obtain oil, water and a noncondensable gas, wherein the oil and the noncondensable gas are used for combusting to obtain the high-temperature flue gas, and the solid residues are discharged out of the heating cavity. According to the method, the heating cavity is indirectly heated by using the high-temperature flue gas, so that the initial materials inside the heating cavity are subjected to thermal decomposition, solid residues free of oil, the noncondensable gas and oil are obtained from the mixed steam generated by thermal decomposition after a series of treatments, and then the noncondensable gas and oil are used for combusting to generate the high-temperature flue gas. Compared with the prior art, the method disclosed by the invention has the advantages that decomposition is carried out without adding a cracking agent, and thermal decomposition can be directly carried out on the oil field wastes in different regions, therefore, the method and the system are better in universality.