Abstract: Slug calorimeter is widely used in thermal protection tests,and lateral heat conduc-tion is one of the most important sources of heat flux measurement error using a slug calorime-ter.An improved adiabatic structure is designed based on slug calorimeter heat transfer analysis, and a heat loss correction method is proposed based on semi-infinite body assumption.FEA(Fi-nite Element Analysis)model is developed to study effects of thermal contact resistance (TCR) between the slug and the adiabatic structure on data reduction results.If TCR is large (R= 1 × 10-3 m2 ·K/W),the max measurement error is less than-9% without correction and more than 20% with correction.On the other hand,when TCR is small (R= 1 ×10-4 m2 ·K/W),the error is about-20% without correction and less than 1 .5% with correction.It is concluded that the correction method can only used in the situation when TCR can be neglected.Numerical simula-tion results also show that using the improved structure with a metal sharp wedge structure add-ed near the surface of adiabatic layer,the max temperature of adiabatic material decreases from o-ver 2000℃ to less than 300℃,which means that with the improved structure,the adiabatic ma-terial is protected efficientlly from ablation.The heat transfer area between the metal wedge and the slug is only about 2 .9% of the total lateral area,which hardly effects selection of data reduc-tion methods.