This paper focused on flame shape and burning rate of n-heptane pool fires beneath an arced ceiling. To investigate the influence of constraint effect, a sequence of scale-model experiments were conducted with varying transverse fire locations. Also, the different pool aspect ratios and layouts were also considered. The results showed that the flame front produced vortices beneath the arced ceiling owing to the restriction of the curved ceiling structure for the transverse flame propagation. As the transverse clearance was reduced, the air entrainment deviated the flame away from the vertical direction. Meanwhile, it was demonstrated that the fuel burning rate presented a non-monotone variation, which means the fire attached to the sidewall did not obtain the peak value, but rather that near the sidewall. In addition, the sidewall constraint accelerated the boiling occurrence of pool fires because a smaller clearance owns a stronger radiation heat feedback and heat transfer to fuel, thus resulting in a earlier boiling time. However, it was also found that the development of the wall fire was mainly restricted by the air entrainment so that its burning rate at steady state occurred a significant reduction.