Abstract: Under the background of the continuous integration between algorithm and finance, the application of algorithm in the financial sector not only stretches the whole financial service chain, but part of the financial transactions is actually placed at the design and development stage of the algorithm, thereby the trust objects of financial consumers are changed. And it also brings the issues concerning the expansion of the traditional fiduciary duties in the financial sector and the expansion boundary. Faced with the financial innovations brought by scientific and technological changes, on the one hand, the intervention factors of algorithmic decision-making should be fully considered, the principle of penetration should be combined to further clarify the subject of responsibility of the fiduciary duty, and the relative legal accountability mechanism should be improved; on the other hand, it is necessary to combine the commonness and individuality of algorithmic governance in the financial field, and on the premise of clarifying the general governance thoughts, the specific contents and responsibility assignments of the fiduciary duties should be constructed differently according to the different models of financial business and the different roles of the main bodies.

Key words: fiduciary duty, financial application, algorithm power, border expansion, accountability mechanism