With the development of ultra-high-voltage（UHV） power grid in China

people have paid more and more attention to electromagnetic pollution in transformer substations caused by power equipments.Therefore

evaluation of electromagnetic field of power equipments becomes increasingly important.According to the national standard

measurement of electromagnetic environment in a 500 kV transformer substation was conducted

and the shielding effectiveness was computed based on the measured data.Results indicate that the current shielding uniform can almost completely shield the electric field

however the uniform has weak shielding effectiveness against magnetic field.The shielding effectiveness（SE） against electric field is 39.4 dB and 12 dB respectively at head and chest of the model

and the SE against magnetic field is 0.09 dB and 0.15 dB respectively

which indicate that the design of UHV shielding uniform should consider shielding power frequency magnetic field.