Comware

Let me give you back ground first. We had flat network for many years and as we growing, we are adding more switches and more remote office locations.  Sonicwall handles all traffic including LAN routing. I would like to use 6200yl switch as core switch. All switches are now connected to 6200yl switch physically but Sonicwall do all the routing.  I would like to use my main swith (HP 6200yl) for all LAN traffice.  Here it is my question.  What is the best practice?

Second question, I create test vlan and didn't work. Here it is what I did. 

#1. Setup VLAN between Sonicwall and Port on main switch, untagged the port that connect to sonicwall, and assigned the 32 subnet ip address.  Set up static routing table on Sonicwall and Hp switch to point each other.  

#2, Create new VLAN with 24 subnet address on HP switch and set route to point #1 vlan,  

#3, setup DHCP on Windows server and tagged the vlan, and untagged one port for client laptop.

#4. Client gets the DHCP address corespoding with VLAN IP, but no Internet. can ping gateway of vlan, but can't ping DHCP server. 

What did i missed? 

You've probably missed some routing.

I hope you have a good network diagram - making this change will be much easier if you have a clear diagram showing all the physical links, VLAN switchport assignments, and VLAN interface IP addressing.

You need a default route on your new core switch, pointing at the Sonicwall.
You need routes on your Sonicwall for each of your internal subnets, pointing at the new core switch