The pH effect on H-aggregation of two aZO polyelectrolytes PNAPE and PEAPE was studied by using UV-Vis spectroscopy．Experimental results showed that the existing states and UV-Vis spectroscopic character were closely related with the ionization degree of the carboxylic groups of the two polymers．The pH range of the azo polyelectrolyte solutions can be divided into three parts．In the pH area where the carboxylic groups initially ionized

the solution was unstable and not discussed here；in the pH area where the carboxylic groups fully ionized

the λmax had little change with pH decrease；in the pH area where the carboxylic groups partly ionized

the λmax showed an obvious red-shift with pH increase because of deaggregation of the H-aggregates of the azo chromospheres of the azo polyelectrolytes．The deaggregation of H-aggregates of azo chromospheres had significant influence on their photo-responsive behavior

which was characterized by increasing both the trans-to-cis isomerization rate and isomerization efficiency with pH increase．