试试这个，可能会有帮助

已转换为CSV文件image ID 和alter text

1. run this code for one time only

$row    = 1;
if( ($handle = fopen ( "Book1.csv", "r" )) !== FALSE ) {
    while ( ($data = fgetcsv ( $handle, 1000, "," )) !== FALSE ) {
        $image_id       = $data[ 0 ];
        $image_alt_text = $data[ 1 ];
        update_post_meta ( (int) $image_id, \'_wp_attachment_image_alt\', $image_alt_text );
    }
    fclose ( $handle );
}