The invention provides a 
seawater desalination preparation device, comprising a water inlet unit (a), a pretreatment unit (b) and a 
reverse osmosis unit (c) which are connected according to the water inflow sequence, wherein, the water inlet unit (a) is used for sending 
seawater to be desalinized to the pretreatment unit, and the 
seawater to be desalinized is drainage of uniflow circulated cooling water from an 
electric power plant; the pretreatment unit (b) comprises a 
precipitation device and a 
filtration device which are connected according to the water inflow sequence, wherein, the upper 
stream of the 
precipitation device is connected with a water inlet unit, while the down 
stream of the 
precipitation device is connected with the 
filtration device; and the 
reverse osmosis unit (c) comprises a boost device, an 
energy recovery device and a 
reverse osmosis device which are connected according to the water inflow sequence, wherein, the upper 
stream of the boost device is communicated with the 
filtration device in the pretreatment unit, while the down stream of the boost device is communicated with the reverse 
osmosis device. The 
seawater desalination preparation device has low cost, thereby the device can be popularized in a large scale and protect environment with scale merit, and can be used for preparing 
ultrapure water.