The invention discloses a process method and a special device thereof for carrying out the continuous separation of gas, liquid and solid phases of reaction solution and carrying out the continuous circulation of the settled catalyst in the TDA synthesis process, wherein, the process method comprises the following contents: the reaction solution which is discharged from a reactor (1) enters a separator (2) via a flow control valve (6), the separation of gas, liquid and solid phases is continuously carried out in the separator (2), and a solid catalyst is recycled; the special separator (2) adopts a two-layer structure, the main body of an outer-layer shell body (14) is a cylindrical shell body (7), the lower part of the cylindrical shell body (7) is a conical structure (13), a settlement body (8) is arranged in the cylindrical shell body (7), and a settlement plate (12) is arranged in the settlement body (8). The application of the method and the special device thereof can realize the continuous separation and circulation of the solid catalyst and the continuous feeding in the TDA synthesis process, thereby stabilizing the operation and improving the efficiency.