The interatomic potential function for the Fe-Cr-V-Ni-Si-C system multi-component alloys was constructed by fitting to the data of this alloy system via quantum chemistry ab initio calculation , first-principlespseudopotentials calculation and least squares method. The stability of the austenite matrixs of Fe-Cr-V-Ni-Si-C system alloys was examined by the acquired interatomic potential functions. The effect of Ni element on the stability of the alloy matrix was studied. The results of calculation show that the stability of austenite matrix with nickel content in the range of 1.02—2.03wt% increases with the increase of nickel content. When the nickel content in the alloys increases to 2.88 wt%, the austenite matrix energy increases and the stability of the austenite matrix decreases accordingly. The austenite matrix energy of N5—N8 alloy is lower than the energy of its martensite phase. Therefore, the microstructure of N5—N8 alloy tends to be of austenite-type. Analysis by XRD indicates that the matrix of N5—N8 alloy is mainly the austenite phase, complemented by martensite. The calculation results agree with the results of XRD.