With the increase of expanded functions, Open CNC system is getting overstuffed gradually, which leads to the decrease of flexibility and reliability. Also, it is hard for users to define their special functions of CNC system. The paper proposes a strategy of intelligent reconfiguration based on floating hierarchical structure. The stepwise control structure of CNC system is broken and a reticular structure is built. Each function unit is assigned a code-array representing its layer levels. By changing values of the code-arrays, the system adjusts layer levels of the function units to adapt change of external environment. Redundant structure and technology of switch circuit are applied to establish internal structure of function unit. Technology of redevelop based on self-conducted configuration and structured language description is put forward. Strategies of simulation and evaluation are applied to prevent the CNC system from being damaged by improper redevelop.