Provided is a method for preparing a reduced titanium powder by a multistage deep reduction, including the following steps of: uniformly mixing a dried titanium dioxide powder with a magnesium powder to obtain a mixture, adding the mixture in a self-propagating reaction furnace, triggering a self-propagating reaction, obtaining an intermediate product of which low-valence titanium oxides TixO are dispersed in an MgO matrix, leaching the intermediate product with a hydrochloric acid as a leaching solution, performing filtering, washing and vacuum drying to obtain a low-valence titanium oxide TixO precursor, uniformly mixing the low-valence titanium oxide TixO precursor with a calcium powder, performing a pressing to obtain semi-finished products, placing the semi-finished products in a vacuum reduction furnace for a second-time deep reduction, and leaching a deep reduction product with a hydrochloric acid as a leaching solution so as to obtain the reduced titanium powder.