看来你是想在目录LastWriteTime的基础上做这个，但是你没有在Get-ChildItem上提到-Directory.

It seems that you want to do this on the basis of the directory LastWriteTime, but you did not mention -Directory on Get-ChildItem.

[cmdletbinding()]
Param()

$TargetFolder = "C:\Users\lit\Documents"
$Folders = Get-ChildItem -Path $TargetFolder -Directory
$Days = 80

foreach ($Folder in $Folders) {
    if ($Folder.LastWriteTime -lt (Get-Date).AddDays(-$Days)) {
        Write-Verbose "Deleting directory $($Folder.FullName)"
        Remove-Item -WhatIf "$($Folder.FullName)" -Recurse -Force
    }
}