The invention discloses a method for preparing a brake pad friction material by using rice and wheat straws and relates to the technical field of composite materials. The brake pad friction material has the following formula: 15 percent of toughened fibers, 16 percent of modified resin, 14 percent of a friction increase agent, 9 percent of sulfur and tin powder, 1.6 percent of carbon black, 2.5 percent of zinc oxide, 8.9 percent of barium sulfate, 10 percent of rice and wheat straw carbon powder, 6 percent of aluminum hydroxide, 14 percent of modified li beads and 3 percent of zinc stearate. The materials are uniformly mixed and stirred, pressed in a mold and subjected to machining such as grinding and chamfering according to a technical requirement to obtain a braking pad. According to the method, the rice and wheat straws are used as raw materials to prepare carbon powder which replaces graphite in a friction material formula, so that the atmospheric pollution caused by severe combustion of straws in each year is alleviated, the production cost of the brake pad is reduced, and the brake performance and the braking effect are enhanced; the friction coefficient is stable; the brake pad is simple in structure, low in brake noise, environment-friendly and pollution-free.