Inside your post loop you can do;

 if ( has_post_thumbnail()) {
 echo get_the_post_thumbnail($post->ID, \'thumbnail\');
 }

这将首先检查是否存在特征图像，如果存在，将以设置/媒体选项中设置的默认“缩略图”大小显示一个特征图像。

This would also work within your loop;

 if ( has_post_thumbnail()) {
 the_post_thumbnail(\'thumbnail\');
 }

This would work (but can be used outside of your loop);

 $id = get_the_ID();
 echo get_the_post_thumbnail($id, \'thumbnail\');

除此之外，还有其他功能可以帮助您自定义尺寸，以满足您的需求。但是，上述默认值为150x150。

阅读：get_the_post_thumbnailthe_post_thumbnail