The problem of signal layering often occurs in Dewar testing of InSb infrared focal plane arrays (IRFPA)detector, affecting the yield of device manufacturing. The cause of the detector signal layering was found by testing the level graph of the Dewar, I--V curve and the substrate doping concentration.Further theoretical analysis also shows that local high-concentration doped regions on the indium antimonide substrate will affect device performance. Based on this research, we can take corresponding measures during the preparation of the chip to minimize the ineffective work in the subsequent processes and improve the tape-out efficiency of the indium antimonide focal plane device process line.