The invention provides a lithium-phosphorus-oxygen-nitrogen modified silicon-carbon composite material and a preparation method thereof. The preparation method comprises the following steps: ball-milling and mixing silicon powder and silicon monoxide powder to obtain mixed powder SiO, x being larger than 0 and smaller than 2; ball-milling and mixing the mixed powder SiO and lithium phosphatepowder to obtain a mixed precursor; sintering the mixed precursor in an atmosphere containing a nitrogen source to obtain a modified precursor; and adding an organic carbon source into the modified precursor, and carrying out sintering in an atmosphere containing argon to obtain the lithium-phosphorus-oxygen-nitrogen modified silicon carbon composite material. When used as a negative electrode ofa lithium ion battery, the silicon-carbon composite material obtained by adopting the technical scheme has low negative electrode resistance, high lithium ion conduction rate, high structure stability and high capacity retention ratio, and endows the lithium ion battery with high first-time charging and discharging efficiency, better cycle performance, long cycle life and higher safety performance.