Provided is a free-space optical signal alignment and transmission device, system, and method. The alignment and transmission device includes an optical engine and a collimating lens module which are connected. The optical engine converts an electrical signal into an optical signal and includes a base board, and a laser driver chip, a laser, a lens array module, a photodiode, and an electrical signal amplifier chip that are provided on the base board; the collimating lens module collimates and sends the optical signal transmitted from the optical engine to free space for transmission, and further shapes and sends the optical signal received from the free space to the optical engine. The laser is connected to the laser driver chip and the lens array module. One end of the photodiode is connected to the lens array module, and the other end thereof is connected to the electrical signal amplifier chip.