This article analyzes what causes the lower main steam temperature of 1# boiler in the PZH-Steel Plant, then designs reconstructive project of spout of burning device which will be up and diameter of tangent round which will be decreased. At the same time, it is analyzed through numerical value stimulation and usual thermal calculation of boiler, and the result of calculation is used to reconstruct the actual boiler. The result of reconstructive run experiment shows that numerical value stimulation was correct, and attains anticipated object.