Ultrapure water preparation apparatus and method

The invention discloses an ultrapure water preparation apparatus and method. The ultrapure water preparation apparatus comprises a source water tank, an ultrafiltration tank and an ultrapure water tank, wherein a precision filter and an ultraprecision filter are connected successively in series between the source water tank and the ultrafiltration tank by using a pipe; and an RO unit and an EDI electronic desalting device are successively disposed between the ultrafiltration tank and the ultrapure water tank. Source water enters into the source water tank; after being output by a source water pump, the water flows through the precision filter and the ultraprecision filter successively; and after particle impurities are filtered out, the water enters into the ultrafiltration tank. The water in the ultrafiltration tank is pumped out by a booster pump, and flows into the RO unit for filtration of impurities, such as mineral impurities, bacteria and virus. The water is desalted by the EDI electronic desalting device, and finally the water enters into the ultrapure water tank, so that the ultrapure water that is low in conductivity is produced, and thus can be used in electrified water-washing operation for washing insulation members of transformation equipment.