网站根目录新建 .htaccess 

RewriteEngine On 

RewriteCond %{SERVER_PORT} 80 

RewriteRule ^(.*)$ https://%{HTTP_HOST}/$1 [R,L]

RewriteEngine On 

RewriteCond %{SERVER_PORT} 80 

RewriteCond %{HTTP_HOST} ^example.com [NC,OR] 

RewriteCond %{HTTP_HOST} ^www.example.com [NC] 

RewriteRule ^(.*)$ https://%{HTTP_HOST}/$1 [R,L]

高级用法 (可选）

RewriteEngine on 

# 强制HTTPS 

RewriteCond %{HTTPS} !=on [OR] 

RewriteCond %{SERVER_PORT} 80 

# 某些页面强制 

RewriteCond %{REQUEST_URI} ^something_secure [OR] 

RewriteCond %{REQUEST_URI} ^something_else_secure 

RewriteRule .* https://%{SERVER_NAME}%{REQUEST_URI} [R=301,L] 

# 强制HTTP 

RewriteCond %{HTTPS} =on [OR] 

RewriteCond %{SERVER_PORT} 443 

# 某些页面强制 

RewriteCond %{REQUEST_URI} ^something_public [OR] 

RewriteCond %{REQUEST_URI} ^something_else_public 

RewriteRule .* http://%{SERVER_NAME}%{REQUEST_URI} [R=301,L]