adm/shop_admin/orderlist.php 주문내역 처리파일에서 버튼을 추가 해보세요
전체 주문내역  이부분바로 아래 에 
<a href="./orderlist_excel.php?<?php echo $qstr1; ?>" class="ov_a">주문엑셀다운로드</a>
이렇게 추가해주시고

orderlist_excel.php 파일생성하시고 아래 복사하여 엑셀 헤더 파일을 정의해주세요  
테스트는 5.6.26 버전 확인되었습니다.
<?php
include_once('./_common.php');
auth_check_menu($auth, '400400', "r");
// 검색조건 동일 적용
$where = array();
$od_status = isset($_GET['od_status']) ? $_GET['od_status'] : '';
$search = isset($_GET['search']) ? $_GET['search'] : '';
$sel_field = isset($_GET['sel_field']) ? $_GET['sel_field'] : '';

if ($search && $sel_field) {
    $where[] = " $sel_field like '%$search%' ";
}
if ($od_status) {
    $where[] = " od_status = '$od_status' ";
}

$sql_search = "";
if ($where) {
    $sql_search = " where ".implode(" and ", $where);
}
$sql = "
    select 
        od_id,
        mb_id,
        od_name,
        od_tel,
        od_hp,
        od_receipt_price,
        od_status,
        od_time
    from {$g5['g5_shop_order_table']}
    $sql_search
    order by od_id desc
";
$result = sql_query($sql);

header("Content-Type: application/vnd.ms-excel; charset=utf-8");
header("Content-Disposition: attachment; filename=orderlist_".date("Ymd").".xls");
header("Content-Description: PHP Generated Data");
echo "\xEF\xBB\xBF"; // 한글 깨짐 방지
echo "<table border='1'>";
echo "
<tr>
<th>주문번호</th>
<th>회원ID</th>
<th>주문자</th>
<th>전화</th>
<th>휴대폰</th>
<th>결제금액</th>
<th>주문상태</th>
<th>주문일시</th>
</tr>
";

while($row = sql_fetch_array($result)) {
    echo "<tr>";
    echo "<td>{$row['od_id']}</td>";
    echo "<td>{$row['mb_id']}</td>";
    echo "<td>{$row['od_name']}</td>";
    echo "<td>{$row['od_tel']}</td>";
    echo "<td>{$row['od_hp']}</td>";
    echo "<td>{$row['od_receipt_price']}</td>";
    echo "<td>{$row['od_status']}</td>";
    echo "<td>{$row['od_time']}</td>";
    echo "</tr>";
}
echo "</table>";
?>