The environment is wamp3 and apache is 2.4. When using wamp2.5 before, the documentroot was designated as h:demo (there is no index.php or the like in the main directory). Every time you open localhost, it is a directory of all projects. After updating wamp3 this time, I found that opening localhost was not found, but typing localhost/test/ can open the project (there is index.php under test), indicating that the configuration of documentroot is correct. I checked how to display the apache directory.
The answer is that in http.conf
Options Indexes FollowSymLinks
But I found that I have this item

<Directory "H:/Demo">
    #
    # Possible values for the Options directive are "None", "All",
    # or any combination of:
    #   Indexes Includes FollowSymLinks SymLinksifOwnerMatch ExecCGI MultiViews
    #
    # Note that "MultiViews" must be named *explicitly* --- "Options All"
    # doesn't give it to you.
    #
    # The Options directive is both complicated and important.  Please see
    # http://httpd.apache.org/docs/2.4/mod/core.html#options
    # for more information.
    #
    Options Indexes FollowSymLinks

    #
    # AllowOverride controls what directives may be placed in .htaccess files.
    # It can be "All", "None", or any combination of the keywords:
    #   AllowOverride FileInfo AuthConfig Limit
    #
    AllowOverride all

    #
    # Controls who can get stuff from this server.
    #

#   onlineoffline tag - don't remove
    Require local
</Directory>