Hi @Polite_Muon , thank you for your reply! You help me solve this problem.
The WalkSensitivity(its value = 5) is just a float variable to adjust the speed. I would have set it as an another slider-controlling value. Regarding your last question, each my character is the only player for its level, that is to say, their will appear when their levels start, so I don’t think I alter their speeds before they are added into the level.
The reason why I failed seems I didn’t call an event to put speed in before. Now I change it, and I will show you below.
Now I add one custom event named “Speed Value” in my character BP
And then I call this event in my widget BP, everything works now.
Thank you again for you reply! I am pretty new to BP and now I know I should use event calling in this case.