Abstract: To study the effects of tube array arrangement on the sound transmission in boiler heat exchangers, the band gap width of transmitted wave after tube arrays in in-line and staggered arrangement was calculated and verified respectively using Matlab and Comsol software, based on phononic crystal theory, by reasonably setting the longitudinal pitch, transverse pitch and size of the tube array as well as the environmental temperature. Results show that after sound passing through tube arrays, acoustic band gap will be produced, and the center frequency of first band gap in T-X direction has relations to the tube array structure and the environmental temperature; the band gap width is related to the filling rate, and generally the sound transmission property under staggered arrangement is worse than under in-line arrangement; for a fixed filling rate, the frequency of sound insulation under staggered arrangement is higher than in-line arrangement; the width of first band gap increases with rising filling rate under in-line arrangement, and the largest width of band gap appears under staggered arrangement at the filling rate of 0.38; the sound insulation effect under staggered arrangement is better than in-line arrangement in a filling rate range below 0.23.