Arduino+dwm1000 distance error more than 50cm ,what kind of method can solve

I use Arduino UNO to get the distance between Tag and Anchor, I use the base code from GitHub.
but distance error more than 70cm, what happens, and what I need to do to decrease the error.
thank you for your help.

Is the error constant? The most common reason for a constant offset is an error in the antenna delay calibration value that you are using.
Either you can change the code to program a different value into the decawave chip or you can simply add/subtract the correct amount in your own code.