Apparatus losing heat by fitting with heat pipe embedded in honeycomb sandwich panel.This article aimed to analyze the factors affecting the heat pipe area flatness in honeycomb sandwich panel.The dimensional precision of honeycomb core and the uneven thickness of adhesive film panel after curing are the main causes. The main solution carried out is increasing the thickness of average pressure tooling board, which can compensate the parts' cumulative dimensional deviation by adhesive film. The results showed that method could be applied to practical production.