The invention discloses a two-dimensional signal modulation and demodulation device and method for reverse modulation spatial optical communication. The device comprises an inquiry end and a reverse modulation end. The reverse modulation end modulates the amplitude of an optical signal by controlling the transmittance of a liquid crystal light valve, and then secondarily modulates the phase of theoptical signal by the vibration of a piezoelectric ceramic. The inquiry end demodulates an optical signal reflected by an echo, can demodulate a signal amplitude change by direct detection, and can demodulate signal phase information by coherent detection and a signal processing module so as to achieve signal transmission at a higher rate than single amplitude modulation or phase modulation. Thedevice and method realize two-dimensional modulation of the optical signal at the reverse modulation end, and demodulate the signal at the inquiry end so as to achieve reverse modulation spatial optical communication at a higher rate.