Disclosed are a multiple-cavity oil pressure constant power heating system device with parallel connection double overload protection and a method. The device comprises an inlet main oil circuit, an outlet oil returning circuit, a control oil circuit, internal protection oil pressure even temperature heating devices and a main oil circuit emergency protecting block. The internal protection oil pressure even temperature heating devices and the main oil circuit emergency protecting block are correspondingly connected with the inlet main oil circuit and the outlet oil returning circuit in parallel. The main oil circuit emergency protecting block communicates with the control oil circuit and is connected with the outlet oil returning circuit. The even temperature heating and local protection of the system are achieved through overload control oil holes of heating section ring blocks in the internal protection oil pressure even temperature heating devices, and bypasses of all the internal protection oil pressure even temperature heating devices are formed through the main oil circuit emergency protecting block to achieve the protection of the system. the multiple-cavity oil pressure constant power heating system device with the parallel connection double overload protection has the advantages that 1, the constant power of multiple-cavity oil pressure is used to achieving heating; 2, parallel connection is adopted, so that the total heat of the system keeps invariant; and 3, local and systematical double overload protection is achieved, so that the safe operation of the system is guaranteed.