In order to study the problems that the measured value of the intensity of the power field in high humidity area is larger than the actual value，this paper starts from the influence of environmental humidity on the electrical characteristic parameters of wood insulating brackets in measurement system，describes the electrical characteristics of wood insulating brackets using complex permittivity，and builds quasi-static field solution model. Finite element method （FEM） is applied to solve the spatial electric field distribution under the transmission line，and the influencing law of environmental humidity on the measurement results of space electric field is obtained by numerical simulation. The research shows that under the actual working conditions，the environmental humidity affects the electrical conductivity of the insulating brackets through changing the moisture content of wood，which distort the spatial electric field near insulating brackets，which is the main factor leading to the increase of electric field strength. Based on the results of calculation and experiment，a method for measuring the intensity of emergency power frequency electric field using metal brackets in high humidity area and correct the results is proposed.