Abstract: Passive non-contact detection technique based on human heart electric field has many merits, i.e., high anti-interference, no radiation, well-concealment, operation easily and so on. Firstly, we deduced the cardiac source potential from single myocardial cell by the traditional heart dipole model; Secondly, we established the simulations of heart-torso and equivalent impedance coupling circuit to obtain the transfer function and attenuation gain of the cardiac electric field from intra-body to body surface; What is more, we acquired the detection formula of human heart electric field taken from simulation analysis of the electric field detection function for point charge model of torso, respectively. The results indicats that individual cardiac electric field can be equal to the electric field produced by the point charge within the error range. Finally, we obtained the theory detection distance based on the passive non-contact detection of individual cardiac electric field.