The invention relates to an in-situ TiB2 and Ti5Si3 composite material and a preparation method thereof. The composite material comprises in-situ TiB2 and Ti5Si3, wherein the in-situ TiB2 is 1 to 20 percent based on the mass of TiB2. The preparation method comprises the following steps: 1) mixing B powder, Si powder and Ti powder, which serve as reactants, uniformly according to a certain proportion and pressing the reactants into billets; 2) preheating the reactant billets in an argon atmosphere and then heating the reactant billets again until a combustion synthesis reaction occurs, or igniting the bottom end of the reactant billets by using arc heat generated by a tungsten electrode to initiate the combustion synthesis reaction; and 3) after the reaction, pressurizing and compacting the reaction product to form the TiB2 and Ti5Si3 composite material. The material has the advantages of excellent performance such as high strength and high hardness, obvious reinforcement effect due to metallurgical combination between reinforcements and a matrix, convenient preparation process, simple equipment, low energy consumption and easy popularization and application.