具体指代含义不同。be made up of的意思是由…构成，一般是多种构成；be made of的意思是由…制成，一般是指材料不发生化学变化、可看出原料的。
be made up of和be made of的例句
Water was made up of oxygen and hydrogen.
水由氧气和氢构成。
Our class is made up of six groups.
我们班由六个小组组成。
The desk is made of wood.
桌子是用木头制的。
The kite is made of paper．
风筝是用纸做的.
The table is made of wood.
桌子是用木头制的。