UCC28180: Output AC800V/10A , using transformer, Is it feasible ?

Your AC input voltage is 800V RMS? and you want to step down to 450V using UCC28180? Is this correct?

AC input voltage is 220V,  get the DC bus 450V voltage by UCC28180.

then pass it through a full bridge and transformer, and finally pass it through LC filtering.

Finally get the AC800V/10A (RMS) output .

In theory, you can. But your PFC stage design is not the most efficient one. I'd recommend totem pole PFC topology instead of boost for this power level (>8kW). You may have to go to interleaved

But your PFC stage design is not the most efficient one------How to design the most efficient ? 

if the design of PFC stage is the most efficient (such as the bus voltage 700V), can the transformer be used in the post stage ?

Boost PFC at 8kW level is less efficient than Totem Pole PFC. 

OK,  get the DC bus 450V voltage by UCC28070(Interleaving CCS).

then pass it through a full bridge and transformer, and finally pass it through LC filtering.

Finally get the AC800V/10A (RMS) output .

Is that ok ?

It definitely a more manageable solution 

So, this is ok ?