The invention discloses a derailment prevention bogie based on bearing saddle positioning detection and a derailment detection method. The derailment prevention bogie comprises axle box positioning devices, side frame components, swing bolster components, foundation brake gears and wheel axle components, wherein a bearing saddle is installed between each side frame component and each axle box positioning device; and the derailment prevention bogie also comprises derailment detection devices installed on the inner side surfaces of four bearing saddles. In addition, the invention also provides the derailment detection method. According to the invention, by additionally arranging the derailment detection devices on the bogie, an early-warning function before derailment of railway vehicles is realized, the problem that the derailment of the railway vehicles cannot be predicted is solved, and guarantee is provided for ensuring railway transportation safety and reducing freight vehicle derailment accidents.