The invention discloses a process of plasma composite process to form chrome-carbon-nitrogen surface alloy under low temperature, which is characterized in that under the condition of the temperature lower than 700 DEG C, firstly, the ion-nitrocarburising or ion nitrading process is performed, then the plasma chromizing process multiple-step composite is performed, or simultaneously the chrome-carbon-nitrogen nitridecarboning is performed, and chrome-carbon-nitrogen alloy layer is obtained on the surface of the nitridecarboning workpiece. The invention has the advantages that the chromizing temperature is reduced from the phase transformation point converted from the ferrite to the austenite to the temperature under the phase transformation point, the energy source and the resources are conserved, the process is simplified, and the operation is convenient; a surface strengthened layer with controllable component of chrome alloy element and nonmetal element such as carbon and nitrogen is reliably formed; the entire composite process adopts the advanced plasma glow discharge technology, the equipment is compact, the technology is suitable, and the operation is convenient, and the invention is advantageous for the popularization and application of the technology.