1, switch the computer input method to QQ Pinyin input method;
2. Place the mouse cursor anywhere in the status bar of QQ Pinyin Input Method, and then click the right mouse button;
3. In the pop-up page, click "Symbol Input";
4. Then click "Special Symbol";
5. After entering the symbol input device, click "Number/Unit" on the left, and the symbol ∞ will appear in the fourth line on the right. Click Select and enter.