To effectively detect electric field of ship, the mathematical model of electric field are established, and the problem of countermeasure of electric field detection is pointed out. Based on the character of gradient and quadratic gradient of electric field, choosing quadratic gradient of vertical orientation as feature, the method of detection is adjusted and the effect of improving detection is calculated. The results of calculation prove that the method can obviously improve the characteristic of countermeasure during detecting electric field of ship, and increase detecting range.