The invention discloses a high-toughness conductive type polycrystalline diamond composite sheet and a preparation method thereof, and belongs to the field of materials science. The high-toughness conductive type polycrystalline diamond composite sheet is prepared by taking silicon-coated diamond micro powder, carbon fibers, diamond micro powder and iron-nickel alloy powder as a powder mixture, and sintering the powder mixture with a hard alloy through a conventional hexahedral top large-cavity press under conditions of pressure being 5.5GPa-6.0GPa and a temperature being 1500-1700 DEG C. Thecarbon fibers and the iron-nickel alloy powder are taken as additives to prepare the composite sheet with high impact resistance and high toughness of the drilling field, so that the comprehensive performance of the PDC composite sheet is improved. Strength, breaking tenacity and impact toughness are further improved to adapt to drilling of various complex ground layers.