我自己解决了这个问题

   <?php
$idObj = get_category_by_slug(\'winners-2018\'); 
$id = $idObj->term_id;
$args = array(
  \'orderby\' => \'name\',
  \'parent\' => $id,
  \'taxonomy\' => \'category\',
  \'hide_empty\' => 1 
  );
$categories = get_categories( $args );


        foreach($categories as $category){
        $cat_archive = get_category ($category);
        //var_dump($cat_archive);
        global $wp_query; 

        $args = array_merge( $wp_query->query_vars,array(       
            \'paged\'=>$paged,    
            \'posts_per_page\'=>10,
            \'post_type\'   => \'winners\',
            \'category_name\' => $cat_archive->slug,
        ));

        ?>
        <div class="outer">
            <div class="inner">             
                <div class="inside">
                    <h1><?php echo $cat_archive->name; ?></h1>

                </div>          
                <div class="left-content winners_fullwidth <?php if(is_category()) { echo $cat_archive->slug;} ?>">
                    <div class="wrap-content clearfix">    
                        <?php
                        $cposts = get_posts(array(
                            \'orderby\' => \'title\',
                            \'order\' => \'ASC\',
                            \'posts_per_page\'=>10,
                            \'post_type\'   => \'winners\',
                            \'category_name\' => $cat_archive->slug,
                        ));
                        foreach ( $cposts as $post ) : setup_postdata( $post ); ?>
                        <div class="press-box">                                
                        <?php if ( has_post_thumbnail() ) { ?>  
                            <div class="art-image">
                                <a href="<?php echo get_permalink(); ?>" title="<?php the_title();?>"><?php the_post_thumbnail( \'square-blog\' ); ?></a> 
                            </div>
                            <?php } ?>                                
                            <div class="art-right">                                   
                                <h2><a class="perma" href="<?php echo get_permalink(); ?>"><?php the_title();?></a></h2>
                                <?php the_excerpt();?>
                            </div> 
                        </div>
                    <?php endforeach;?>
                    <?php wp_reset_query(); ?>  
                    </div><!-- wrap-content -->
                </div><!-- left-content -->
            </div>  
            <?php } ?>
Solution was

    $idObj = get_category_by_slug(\'winners-2018\'); 
$id = $idObj->term_id;
$args = array(
  \'orderby\' => \'name\',
  \'parent\' => $id,
  \'taxonomy\' => \'category\',
  \'hide_empty\' => 1 
  );
$categories = get_categories( $args );


        foreach($categories as $category){
        $cat_archive = get_category ($category);
        //var_dump($cat_archive);
        global $wp_query; 

        $args = array_merge( $wp_query->query_vars,array(       
            \'paged\'=>$paged,    
            \'posts_per_page\'=>10,
            \'post_type\'   => \'winners\',
            \'category_name\' => $cat_archive->slug,
        ));