The invention discloses insulating ceramic for an integrated circuit substrate. The insulating ceramic consists of the following raw materials in parts by weight: 60-80 parts of willemite, 30-40 parts of barium titanate, 20-30 parts of burnt talc, 10-30 parts of titanium dioxide, 10-20 parts of silicon dioxide, 5-15 parts of silicon nitride, 3-8 parts of quartz powder, 5-10 parts of mica powder, 2-8 parts of boron carbide, 5-10 parts of sodium polyacrylate, 8-15 parts of phenolic resin, 3-8 parts of aluminum oxide, 2-6 parts of a compound additive, 1-5 parts of an adhesive and 100-120 parts of deionized water. The insulating ceramic for the integrated circuit substrate, disclosed by the invention, has the advantages of being low in insulation resistance value, good in insulation performance, long in service life, low in production cost and the like; meanwhile, according to a preparation method disclosed by the invention, via strictly controlling process parameters, the structural change and the chemical change of an insulating ceramic material in the sintering process can be controlled, and the requirements for industrial application can be met.