A drilling system including a feed control module, a force control module, a hole breaking control module, a conversion module and a computing unit is provided. The feed control module sets a feed force threshold and a feed speed threshold for the computing unit to determine whether the current mode satisfies a first conversion condition. The hole breaking control module sets a drilling penetration force threshold and a drilling penetration speed threshold for the computing unit to determine whether the current mode satisfies a second conversion condition. The conversion module informs to change the feed force and the feed speed according to the determination results of the two conversion conditions. The force control module provides the feed force. With the drilling system, possible impact on the workpiece due to resistance change which occurs when the drill just touches and nearly gets through the workpiece will be reduced.