I've already have HPE Proliant Gen9 server, and at first I slotted 8 * 16 GB RAM, but Now I need to add more Ram, So is it possible to add 64/32 GB Ram beside the 16 GB Ram?
According to the manual (PDF), page 5:
The 128GB LRDIMM may not be mixed with other DIMM capacities/types.
Same on page 26:
NOTE: Mixing the 128GB LRDIMM with other capacities is not supported.
Since the manual says nothing about mixing 16 GB with 32/64 GB, it should be fine.
Be careful, as always, when choosing the type (registered or not, load reduced or not) and the frequency, and ensure the CPU is compatible with the RAM you want to buy.