QT Creator:how to change the menu font size?

There is no such option. You have to modify the DPI scaling of windows, which will make all "legacy" shell applications appear larger to compensate for the high DPI of the device.

If you don't want to modify the settings, you might want to try running creator with an QT_SCALE_FACTOR=2 env var or so.

Create a startScaled.cmd in creator's exe directory with the content:

@echo off 
set QT_SCALE_FACTOR=2
qtcreator.exe

And use this to start creator up-scaled.

On linux mint for me, changing the desktop DPI scaling doesn't help with QT sidebar font in particular although most other things do scale.

The scale factor variable method does work though. Here's the script I used and just modify the installed menu shortcut for QtCreator to run it instead of directly running the qtcreator executable:

   #!/bin/bash
   #my_qtcreator.sh
   export QT_SCALE_FACTOR=1.5
   /opt/Qt/qtcreator-4.2.2/bin/qtcreator

I had the same nasty problem in Ubuntu , the solution is easy.

1. In the top left menu , choose Tools > Options > Environment

2. Mark the checkbox that says "Enable high DPL scaling"

3. Restart and it should work