A lithography system for an extreme ultra violet (EUV) mask is provided. The lithography system includes a coupling module. The coupling module includes at least one mask contact element configured to touch a peripheral area of the EUV mask. The lithography system also includes an ammeter having an end electrically connected to the EUV mask through the at least one mask contact element and another end connected to a ground potential. The ammeter includes a sensor configured to measure a current conducting from the EUV mask to the ground potential and a compensation circuit configured to provide a compensation current that is opposite to the current measured by the sensor.