Like other silk bedding, there are some cases you should pay more attention when you are washing silk blankets.
Hand-washing should be reserved for smaller blankets that are easier to work with when washing and rinsing. Larger silk blankets can be difficult to rinse and rid of water. If it is small enough, you can roll it up inside of a large towel to aid in extracting the water. After washing, you can lay the blanket flat on a drying rack or hang it in a place out of the direct sunlight. A plastic drying rack is acceptable or any other clean object, but do not use a wooden drying rack as the finish on the wood might stain the blanket.
However, before all the things you do, check the care instructions that came with the silk blanket and do as what it says.