Specific steps:
Log in to QQ on the computer first, then click the penguin icon at the bottom corner of the QQ panel, select Help in turn, and then click to enter my QQ Center, as shown in the following figure:
After entering my QQ Center, switch to the "Dynamic" option, and then click to switch to "My Dynamic", as shown below:
Finally, as you can see here, we have published the history of QQ personalized signature before. When we put the mouse on it, an "X" button will be displayed in the upper right corner. Click it to delete the dynamic, as shown in the figure below: