The invention discloses a method for improving photoelectric property of dye-sensitized solar cells by coadsorbent. The method is characterized by including the steps of (1) coadsorbent solution preparation: adding the coadsorbent into a mixed solution of acetonitrile and tert-butyl alcohol, stirring for 12 hours in the absence of light at the room temperature and preparing the stirred mixture into coadsorbent solution in a concentration range of 0.1-3mM; and (2) photo-anode modification: activating a titanium dioxide porous film calcined at the temperature of 500 DEG C for 30 minutes at the temperature of 150 DEG C, thermostating for 30 min at the temperature of 80 DEG C, then soaking the titanium dioxide porous film in N719 dye with standing for 24 hours, then taking out the titanium dioxide porous film, and cleaning the titanium dioxide porous film with ethyl alcohol prior to drying with cold air; and placing the titanium dioxide porous film adsorbed with the dye in the coadsorbent solution prepared in the step (1), standing for 0.5-12 hours, then taking the titanium dioxide porous film out slowly, and cleaning the titanium dioxide porous film with ethyl alcohol prior to drying with cold air so as to obtain a photo anode modified by the coadsorbent and coated with the titanium dioxide porous film.