Polygraph, as a traditional lie detector, is used to detect lies by some changes of human peripheral neuro-vegetative responses. The reliability of this technique, which depends on some other none-instrumental factors to a great extent, has drawn lots of attention and question. Event related potentials (ERPs) have good specificity and time resolution and can monitor instant cognitive processing and brain electric activity. However, its space resolution is poorer than brain function nuclear magnetic resonance imaging (fMRI) relatively. Brain fMRI can show the brain functional changes directly. It has good space resolution but bad time resolution, and all images of fMRI are just the final results of brain changes after lying. So, fMRI technique for detecting deception is still in the basic research phase at present. Contrary to other techniques, psychometrics has been used and studied more in detecting deception or malingery in practice.