The invention discloses a high-performance LCF/Ni/PA6 composite material with an electromagnetic shielding function, and a preparation method thereof. The composite material comprises, by weight, 59-95% of PA6, 5-25% of long carbon fibers, 0-15% of ultrafine nickel powder, and 0-1% of a flow modifier and an antioxidant. The composite material has the following advantages: 1, long carbon fiber reinforced PA6 prepared through a melt impregnation technology has higher carbon fiber retention length than short carbon fiber reinforced PA6, so the composite material has higher mechanical performances and electric performances under the same carbon fiber content; and 2, electromagnetic pollutions generated by electromagnetic waves emitted by electrons and electric devices have great influences on the body health of people and technologic production, metal used as a shielding material has the disadvantages of large density, poor corrosion resistance and poor processability, and the high-performance LCF/Ni/PA6 composite material prepared through adding the ultrafine nickel powder has an excellent electromagnetic wave shielding effect, and meets requirements of an application in the electrons and electric devices by substituting the metal material.