I know we could bulk update TFS work items with Excel.
However, this time I want to integrate this in my build process. Do it either with TFS API or power shell script. We are working on TFS2017/VS2017
I look forward to any suggestions from your guys.
You could do this through a powershell script based on TFS client API.
PowerShell lets you load any .Net assembly by using the Add-Type cmdlet.
You can then use the classes defined in that assembly inside your PowerShell session. This opens up a wide range of possibilities, one of them being that you can use the TFS API from PowerShell.
After the TFS assemblies have been loaded, we can get a reference to the TPC:
$tfs = [Microsoft.TeamFoundation.Client.TfsTeamProjectCollectionFactory]::GetTeamProjectCollection($tfsUri)
And then the $tfs object can be used to access the required services (the work item store in this case):
$workItemStore = $tfs.GetService([Microsoft.TeamFoundation.WorkItemTracking.Client.WorkItemStore])
For the other things and more detail, you could find the entire script on KeesV's GitHub: TfsBulkUpdateWi.ps1
Another blog for your reference: How to batch update multiple work items in TFS by PowerShell