The porblem is displays have different dpi and if i use them with eyefinity, there will be some issues with image.
And a question is, how can i deal with it to make both displays work together with eyefinity?
For the best Eyefinity experience, it is always recommended to use the same display resolution.
If not, Eyefinity will chose the common resolution, in this case, 1680x1050, leading to the display issues you are experiencing.