The invention relates to a composition used for treating arthritis, and a preparation method thereof, and belongs to the technical field of medical science, skin repairing, and plastic surgery. A blood plasma mixture comprises universal blood plasma and a blood component additive; the universal blood plasma is universal fresh frozen blood plasma or universal frozen dried blood plasma; the universal fresh frozen blood plasma or universal frozen dried blood plasma are prepared from, by volume, 5 to 10 parts of A type blood plasma, 2 to 7 parts of B type blood plasma, 0.5 to 3 parts of O type blood plasma, 0.5 to 3 parts of AB type blood plasma via mixing. The multifunctional human blood plasma can be used for patients with thrombocytopenia, leukemia, and other arthritis. According to an application method, matching is carried out via inputting blood test results and synovial fluid test results into a computer, in vitro blending is carried out, and injection into human body articular cavities is carried out.