This work studied the effect of varying the distance between adjacent two burners (DBATB) in a 600 MWe supercritical down-fired utility boiler incorporating multi-injection and multi-staging. Cold-state tests involving airflow trajectory tracing in an actual boiler with a DBATB of 971 mm and 1:20 scale model tests with DBATB values of 971, 1329, and 1687 mm were conducted to study the effects of adjusting DBATB on aerodynamic characteristic. The results indicate that increasing the DBATB had a minimal effect on the symmetric W-shaped flow pattern. A downward airflow rushing the hopper wall was observed at a DBATB of 971 mm, while increasing the value from 971 to 1687 mm promoted decay of the downward airflow velocity in association with gradually enhanced airflow diffusion toward the furnace center. Simultaneously, the airflow rushing the hopper wall disappeared, while the airflow dimensionless penetration depth and the volume of air flowing into the hopper zone were respectively reduced by 12% and 20%. Increasing the DBATB contributes to prevent the actual downward flame from rushing the hopper water wall and form a more uniform heat release along the furnace width. This effect would be expected to avoid local overheating and bursting of the water-wall tube in an actual operational boiler, and an optimal DBATB value of 1687 mm is recommended for this purpose.