The invention discloses a numerical control system, a control method for the numerical control system and a powering up method for the control method for the numerical control system. The control method for the numerical control system comprises the steps of detecting whether an upper computer is abnormal or not, and outputting preset safety data to a machine tool if the upper computer is judged abnormal. Through the mode, the numerical control system, the control method for the numerical control system and the powering up method for the control method for the numerical control system can prevent indeterminacy states from occurring on numerical control system powering up or the upper computer from when the numerical control system powering up or the upper computer is abnormal, and can prevent damage, caused by the indeterminacy states, on the machine tool.