您不应该设置posts_per_page 值，也不应在查询运行后直接设置对象属性。这将导致对象数据与自身不同步。

您需要在启用筛选器的情况下更改该值pre_get_posts.

function pregp_archive_ppp_wpse_108225($qry) {
  if ($qry->is_main_query() && $qry->is_archive()) {
      $qry->set(\'posts_per_page\',5);
  }
}
add_action(\'pre_get_posts\',\'pregp_archive_ppp_wpse_108225\');

Method 1: You can use pre_get_posts in your functions file to alter the query. This would go in your theme\'s functions.php file.

function limit_archive_posts( $query ) {
if ( $query->is_archive() && $query->is_main_query() && !is_admin() ) {
        $query->set( \'posts_per_page\', 5);
    }
}
add_action( \'pre_get_posts\', \'limit_archive_posts\' );

Method 2: This can also be achieved by placing the following code before the loop in the archive page.

global $query_string;
query_posts("{$query_string}&posts_per_page=5");

If you have used with custom post type like \'news\' then you can use below code for that.You can use pre_get_posts in your functions file to alter the query. This would go in your theme\'s functions.php file.

function limit_news_archive_post_type( $query ){
    if($query->is_post_type_archive(\'news\') && $query->is_main_query() && !is_admin()){
            $query->set( \'posts_per_page\', 5 );
    }
}
add_action( \'pre_get_posts\', \'limit_news_archive_post_type\' );