Abstract: A semiphysical model to predict the thermal ablation traces of PVC plastic plate was established according to the factors which influence the thermal ablation trace formation,and the model was embedded in FDS source code,a program was compiled to reconstruct the wall thermal ablation traces.At the same time,the experiment of PVC plastic plate thermal ablation trace was set up,and using the compiled FDS program to reconstruct the experiment.It showed that the thermal ablation trace of the reconstruction was slightly smaller than the entity experiment in width,and slightly larger in height,but the variation tendency was the same.There was a growth retardation relationship between the width and height of thermal ablation traces and the heat release rate of the fire; there was a linear growth relationship between the width and height of the thermal ablation traces and the burning time; the width and height of the thermal ablation traces decreased with increasing distance between the fire and the wall or the corner.The thermal ablation traces generated by the fire in the corner of the wall was higher and darker than those generated by the fire at the middle of the wall.The results of the reconstruction and the entity experiment were consistent.Combined with other proofs in fire investigation,a chain of mutually supporting evidence could be formed.