The invention discloses negative ion composite powder suitable for building materials. The negative ion composite powder is prepared from the following components in parts by mass: 30-80 parts of liddicoatite powder, 1-8 parts of calcium stearate, 1-5 parts of zinc oxide, 0-30 parts of rare earth, 1-30 parts of zeolite powder, 1-8 parts of monazite powder and 1-3 parts of poly(cellulose ether). The negative ion composite powder provided by the invention has the excellent effects that the negative ion composite powder is simple in preparation process and low in raw material price and has durability, high efficiency and environment friendliness; negative ion plates prepared from the negative ion composite powder can efficiently and stably release 2000-3800 negative ions per s.cm<2> and can conduce to purifying air and eliminating indoor peculiar smell and harmful gases; the negative ion composite powder is an environment-friendly negative ion additive.