Hi,how much will cost send pack from china to poland by sea 20kg?

But each package to Poland should be no more than 15kg weigh, so they should be two parcels. Also no surface mail is available from China to Poland, and then I recommend you use SAL (Surface Air Lifted). It costs 740.80RMB (receipt, service and insurance fees excluded) for 15kg and 295.80 RMB for 5kg.