What should I do if the alphabetical index of my iPhone address book is missing?

Yes. First select all the data, then click "Data - Sort" on the toolbar, and make the following settings in the pop-up dialog box: select "Name" as the main keyword, select the default "Value" as the sorting basis, and select the default "Number" for the order. Ascending", confirm. You can make a drop-down list in Excel and select the situation you want. In iPhone, just press the letter on the far right side of the address book to reach the specified pinyin position.