The utility model relates to an improved milling structure for a drilling machine, which mainly comprises a main shaft sleeve clamping mechanism, a milling cutter mounting and clamping device, a main shaft minim feeding mechanism and a working table clamping device. The main shaft sleeve clamping mechanism comprises a clamping screw rod arranged at the side of the main shaft sleeve, screw nuts fixed on the clamping screw rod, a left clamping block and a right clamping block respectively arranged at the left end and the right end of the clamping screw rod and clamped at one side of the main shaft sleeve, and a clamping handle clamped at one end part of the clamping screw rod. The main shaft minim feeding mechanism comprises a clutch device arranged at a clutch device seat at the lower end of a worm and a hand wheel shaft and a hand wheel connected with the clutch device, and the worm is positioned on a bearing seat. The working table clamping device is a locking device. The table back surface of the working table is provided with a round pin, and the top of a carrier frame is provided with a locking block which can lock the round pin in a lateral movement. The locking block is fixed via screw nails. The utility model perfects the milling function of a drilling and milling machine, improves reliability, practicability and security of a machine tool, and develops a circular column vertical drilling machine into a multifunctional circular column vertical milling and drilling machine.