A disposable tubeless fluid delivery system, which comprises: a button unit configured to receive instructions given by a user through pressing button; a fluid reservoir unit configured to store a fluid; an indwelling unit configured to let through the fluid to a patient when it is implanted in a subcutaneous tissue of the patient, wherein the indwelling unit comprises an indwelling cannula configured to be implanted in the subcutaneous tissue of the patient; a fluid driving unit configured to deliver the fluid stored in the fluid reservoir unit to the subcutaneous tissue of the patient via the indwelling unit, when it receives a delivery instruction; and a control unit coupled to the button unit, the fluid reservoir unit, the indwelling unit and the fluid driving unit, wherein the control unit is configured to, when it receives a button-pressing instruction, output a corresponding delivery instruction to the fluid driving unit; characterized in that: the disposable tubeless fluid delivery system further comprises a key unit (12, 13, 130, 131) comprising a socket and a key insertable into the socket, the key comprises a key shell and a plug embedded in the key shell, and the key unit (12, 13, 130, 131) is configured to output a selection instruction indicating at least one working mode, wherein the at least one working mode is selected from a group consisting of a basal rate delivery mode, a programmable basal rate delivery mode, a delivery suspend mode, a system locking mode and a wireless control mode, and the or each key unit (12, 13, 130, 131) has a prestored working mode; the control unit is further coupled to the key unit (12, 13, 130, 131) and is configured to, when it receives the selection instruction of the working mode, output the corresponding delivery instruction to the fluid driving unit; and the disposable tubeless fluid delivery system comprises a controller and a pump base connected to the controller, wherein the control unit, the button unit and the key unit (12, 13, 130, 131) are set on the controller, and the fluid reservoir unit, the fluid driving unit and the indwelling unit are set on the pump base.. a button unit configured to receive instructions given by a user through pressing button; a fluid reservoir unit configured to store a fluid; an indwelling unit configured to let through the fluid to a patient when it is implanted in a subcutaneous tissue of the patient, wherein the indwelling unit comprises an indwelling cannula configured to be implanted in the subcutaneous tissue of the patient; a fluid driving unit configured to deliver the fluid stored in the fluid reservoir unit to the subcutaneous tissue of the patient via the indwelling unit, when it receives a delivery instruction; and a control unit coupled to the button unit, the fluid reservoir unit, the indwelling unit and the fluid driving unit, wherein the control unit is configured to, when it receives a button-pressing instruction, output a corresponding delivery instruction to the fluid driving unit; characterized in that: the disposable tubeless fluid delivery system further comprises a key unit (12, 13, 130, 131) comprising a socket and a key insertable into the socket, the key comprises a key shell and a plug embedded in the key shell, and the key unit (12, 13, 130, 131) is configured to output a selection instruction indicating at least one working mode, wherein the at least one working mode is selected from a group consisting of a basal rate delivery mode, a programmable basal rate delivery mode, a delivery suspend mode, a system locking mode and a wireless control mode, and the or each key unit (12, 13, 130, 131) has a prestored working mode; the control unit is further coupled to the key unit (12, 13, 130, 131) and is configured to, when it receives the selection instruction of the working mode, output the corresponding delivery instruction to the fluid driving unit; and the disposable tubeless fluid delivery system comprises a controller and a pump base connected to the controller, wherein the control unit, the button unit and the key unit (12, 13, 130, 131) are set on the controller, and the fluid reservoir unit, the fluid driving unit and the indwelling unit are set on the pump base.. the disposable tubeless fluid delivery system further comprises a key unit (12, 13, 130, 131) comprising a socket and a key insertable into the socket, the key comprises a key shell and a plug embedded in the key shell, and the key unit (12, 13, 130, 131) is configured to output a selection instruction indicating at least one working mode, wherein the at least one working mode is selected from a group consisting of a basal rate delivery mode, a programmable basal rate delivery mode, a delivery suspend mode, a system locking mode and a wireless control mode, and the or each key unit (12, 13, 130, 131) has a prestored working mode; the control unit is further coupled to the key unit (12, 13, 130, 131) and is configured to, when it receives the selection instruction of the working mode, output the corresponding delivery instruction to the fluid driving unit; and the disposable tubeless fluid delivery system comprises a controller and a pump base connected to the controller, wherein the control unit, the button unit and the key unit (12, 13, 130, 131) are set on the controller, and the fluid reservoir unit, the fluid driving unit and the indwelling unit are set on the pump base..