The invention relates to a cutting machine and a shield assembly thereof. The shield assembly comprises a shield main body, a supporting arm, a pivoting arm and a pressing plate assembly, wherein the shield main body is used for partially covering a saw blade of the cutting machine; the supporting arm is connected with a bench of the cutting machine and supports the shield main body above the bench; the pivoting arm is connected with the shield main body and rotates around the pivoting shaft relative to the supporting arm so as to ensure that the shield main body is at least in a first working position close to the bench and a second working position away from the bench; the pressing plate assembly is arranged on the shield main body and comprises a workpiece pressing plate vertical to the bench and supporting against the workpiece, the working pressing plate is provided with a pressing plate plane; and the pressing plate assembly also comprises an operable pressing plate regulating mechanism for regulating the movement of the workpiece pressing plate between the two positions relative to the bench. Compared with the prior art, the invention can realize that different thicknesses of workpieces are cut within a certain range without regulating the whole shield assembly, and is convenient and simple in operation.