The invention discloses a method for preparing a bismuth-boron-based flexible catalytic electrode in an organic phase, which comprises the following steps of by taking a metal bismuth-boron compound as a precursor, adding a reducing agent, a complexing agent, a buffering agent and an organic solution, and mixing in proportion to prepare a plating solution, ultrasonically cleaning a substrate material in deionized water, and soaking the substrate material in deionized water, ethanol and acetone in sequence, immersing a flexible substrate material in a metal salt solution, dipping the flexible substrate material in hydroboron for 2s to complete activation of a flexible non-conductive substrate, and washing the flexible non-conductive substrate with deionized water and ethanol in sequence for later use, and immersing the pretreated substrate material into the plating solution prepared in the first step, carrying out chemical plating reaction, taking out the substrate material, and washing with ethanol to obtain the electrode material, namely the product. The preparation method is simple, the universality is better, the manufacturing cost is lower, the concentration can be changed in a larger range, the stability is good, and the requirement on the working environment is low.