The output pow er o f No . 1 boiler ( Y-130/ 39-2) in a pet ro chemical plant is low er t han ex pected fo r a long time . Based on the data from site mea sur ement , this paper analyzes the ca uses fo r the low o ut put and put s fo rw ar d m easur es to impro ve the bo iler o per ation. T he practical r esults show that the analy ses a re rea so nable.