My monitor's resolution is 1600x900, but I found that War3 does not have this resolution option. My monitor is reminding me to set an appropriate resolution.

Return to the Windows system, press Windows + R, type regedit, and open the Registry Editor

Find location:Computer\HKEY_CURRENT_USER\Software\Blizzard Entertainment\Warcraft III\Video

You need to modify the values of reswidth and resheight, which correspond to the horizontal and vertical resolution of the monitor. Double-click to edit, switch to decimal, and just enter your monitor's resolution.

After that, when you open war3 again, it will be the monitor's resolution.