The invention provides a technology device and method for preparing propylene by dehydrogenating 
propane or 
propane-enriching low carbon 
hydrocarbon. The device comprises a reacting / regenerating part and a product fractionating part. A reacting / regenerating 
system is divided into a parallel type arrangement scheme and a coaxial type arrangement scheme by a 
fluidized bed reacting / regenerating technology, wherein a raising 
pipe of the parallel type reacting / regenerating 
system is an internal or external raising 
pipe, and a raising 
pipe of the coaxial type reacting / regenerating 
system is an external raising pipe. The method comprises the steps: leading raw materials and reaction products to enter into a raising pipe reactor after heat exchange; performing a dehydrogenating 
conversion reaction under the conditions that the 
reaction temperature is 500-700 DEG C, the pressure is 0.1-0.4MPa, and the ratio of a microspherical catalyst to oil is 5-60, wherein the microspherical catalyst consists of 
chromium, 
rare earth oxides, 
alkali metal oxides and a gamma-Al2O3 carrier, preferably, the temperature is 550-670 DEG C, the pressure is 0.1-0.15MPa, and the ratio of the microspherical catalyst to oil is 6-14; leading the reaction products and the raw materials to enter into a gas-oil separator to separate a 
gas phase, a 
liquid phase from a water phase after heat exchange and cooling; leading the separated gas to enter into a 
gas compressor to be compressed and be transported to an absorbing / stabilizing part; pumping the liquid to an absorbing 
tower; transporting the liquefied gas from a return tank at the top of a stabilizing 
tower to a propylene / 
propane separating 
tower by a charging pump of a propylene tower; discharging the fine propylene separated from the top of the tower out of the device as a product; discharging the separated byproduct 
hydrogen out of the device; and returning products at bottom of the tower to the reacting / regenerating part to be recycled.