Global XYZ axis

video shows that i should select “Global XYZ axis”,
but when it comes to my blender, it provide + and -,
which should i use?

Video is probably from an older version of Blender, you now have the option to select whether your bone roll follows the Positive axis selected or points in the Negative direction of the chosen roll axis. The only difference you may encounter is that bone rotations may be negative where you expected them to be positive. Try it each way (positive would have been the only way under the older Blender shown on the Tut) and use the easiest for your animation needs.

Cheers, Clock.

I think you will have to post your blend file here.

Cheers, Clock.

Last image shown where reg rotates when pole target is set happens when rigging with Blender. If so recalculate roll will not solve it. Look at this video at time 11:50.