For single landmine detection with the passive infrared imaging technology of the landmine detection, the infrared images were processed according to the 1-D signal detection theory and the algorithms for modern signal processing. The signal models of landmine and background image were given by analyzing the theory of landmine detection on the infrared image and combining the characteristic of the background infrared image. Then, combined with the characteristics of the models’ unknown parameters, we estimated the unknown parameters through the algorithms of modern signal processing. When the landmine and the background image signal were determined, the generalized correlator was used to detect the landmine. Testing results with the single infrared image burying the target show that the method can mark the landmine clearly.