A thiolation method for modifying carbon nanotubes includes steps as follows. A carboxylation step is provided, wherein the carbon nanotubes are reacted with an oxidant for generating carboxyl groups on surfaces of the carbon nanotubes so as to form carboxylated carbon nanotubes. A hydroxylation step is provided, wherein the carboxyl groups are transformed into hydroxyl groups so as to transform the carboxylated carbon nanotubes into hydroxylated carbon nanotubes. A thiolation step is provided, wherein the hydroxylated carbon nanotubes, a sulfur source and a first acidic substance are mixed and then stirred so as to form a first mixture, the first mixture is added portion-wisely into an alkaline solution so as to form a second mixture, and the second mixture is acidified so as to form an acidified solution having a pH value ranging from 2 to 3, thus the hydroxylated carbon nanotubes are transformed into thiolated carbon nanotubes. |