Using Darksend, one Darksend transaction can be splitter into multiple transactions. I think it can make Darkcoin's blockchain growing very quickly.
Is there any solution for it? I have a very bad experience with Bitcoin because loading the full Bitcoin's blockchain take a lot of time.
This is a problem that will hit any coin if it succeeds in making it to the mainstream. There is stuff that can be researched (and implemented if applicable) in the future. The blockchain could be pruned using technologies the Bitcoin researchers will come up with (because Darkcoin is Bitcoin based), 
mini-blockchain could be used, and I even saw a Darkcoin dev team member on the IRC the other night talking about the possibility of using the masternode network to run their own side chain that compresses the main chain blocks or something to that nature.