The invention discloses a method for controlling the generation of fuel coal superfine particles by use of modified kieselguhr. The method comprises the following steps: (1) preparing modified kieselguhr powder, wherein the modified kieselguhr powder contains hydrochloric acid modified kieselguhr powder and polyhydroxyl aluminum modified kieselguhr powder; (2) uniformly mixing the modified kieselguhr powder with coal powder according to a mass ratio of 3:100; and (3) feeding the uniformly mixed modified kieselguhr powder and coal powder into a boiler according to a predetermined speed, and firing, wherein the modified kieselguhr powder inhibits the generation of superfine particles through a physical or chemical effect; and meanwhile, the generated superfine particles are transferred toward large particle size to form particles that can be captured by the dust removal device.