A charging method comprising: conducting a bidirectional communication between a power adapter and a terminal device under control of a communication sequence between the power adapter and the terminal device comprising: transmitting a first instruction to the terminal device, wherein the first instruction is used for querying whether or not the terminal device agrees to activate the fast charging mode; receiving a first reply instruction corresponding to the first instruction from the terminal device, the first reply instruction indicating that the terminal device agrees to activate the fast charging mode; and determining to activate the fast charging mode according to the first reply instruction; transmitting a second instruction to the terminal device after determining to charge the terminal device in the fast charging mode, wherein the second instruction is used for querying whether or not a current output voltage of the power adapter is proper to be a charging voltage corresponding to the fast charging mode; receiving a second reply instruction corresponding to the second instruction from the terminal device, the second reply instruction indicating whether the current output voltage of the power adapter is proper to be the charging voltage corresponding to the fast charging mode; adjusting the current output voltage of the power adapter to be the charging voltage corresponding to the fast charging mode according to the second reply instruction, and transmitting a third instruction to the terminal device, wherein the third instruction is used for querying maximum charging current currently supported by the terminal device; receiving a third reply instruction corresponding to the third instruction from the terminal device, the third reply instruction indicating the maximum charging current currently supported by the terminal device; determining the charging current corresponding to the fast charging mode according to the third reply instruction; adjusting the output current of the power adapter to be the charging current corresponding to the fast charging mode to enter a constant current phase; and charging the terminal device with the output current of the power adapter. conducting a bidirectional communication between a power adapter and a terminal device under control of a communication sequence between the power adapter and the terminal device comprising: transmitting a first instruction to the terminal device, wherein the first instruction is used for querying whether or not the terminal device agrees to activate the fast charging mode; receiving a first reply instruction corresponding to the first instruction from the terminal device, the first reply instruction indicating that the terminal device agrees to activate the fast charging mode; and determining to activate the fast charging mode according to the first reply instruction; transmitting a second instruction to the terminal device after determining to charge the terminal device in the fast charging mode, wherein the second instruction is used for querying whether or not a current output voltage of the power adapter is proper to be a charging voltage corresponding to the fast charging mode; receiving a second reply instruction corresponding to the second instruction from the terminal device, the second reply instruction indicating whether the current output voltage of the power adapter is proper to be the charging voltage corresponding to the fast charging mode; adjusting the current output voltage of the power adapter to be the charging voltage corresponding to the fast charging mode according to the second reply instruction, and transmitting a third instruction to the terminal device, wherein the third instruction is used for querying maximum charging current currently supported by the terminal device; receiving a third reply instruction corresponding to the third instruction from the terminal device, the third reply instruction indicating the maximum charging current currently supported by the terminal device; determining the charging current corresponding to the fast charging mode according to the third reply instruction; adjusting the output current of the power adapter to be the charging current corresponding to the fast charging mode to enter a constant current phase; and charging the terminal device with the output current of the power adapter.