The invention provides an aza-fused conjugated trapezoidal 
polymer. The aza-fused conjugated trapezoidal 
polymer is prepared from 1,2,4,5-benzenetetramine tetrahydrochloride and 2,5-dihydroxy-1,4-
benzoquinone through a 
polymerization reaction, or from 1,2,4,5-benzenetetramine tetrahydrochloride and 
piperazine-2,3,5,6-tetraone through a 
polymerization reaction, or from 1,2,4,5-benzenetetramine tetrahydrochloride and 
pyrene-4, 5, 9, 10-tetraone through a 
polymerization reaction. In the conjugated trapezoidal 
polymer, a fused ring structure limits free torsional motion between aromatic units along a skeleton, stable and effective conjugation can be provided, and transmission of carriers is facilitated. The conjugated trapezoidal polymer has good absorption performance in a visible light range; the energy band structure of the conjugated trapezoidal polymer meets the requirement of water photolysis for 
oxygen production under 
visible light irradiation; the conjugated trapezoidal polymer has excellent 
oxygen production performance; and the trapezoidal polymer is used for visible light 
decomposition of water for 
oxygen production for the first time, and the application scope of the trapezoidal polymer in the field of 
photocatalysis is greatly broadened.