NOVELTY - A microwave-assisted flash pyrolysis system, comprises: at least one microwave generator connected to a chamber; where the chamber comprises: at least one feedstock inlet, at least one first baffle plate, a microwave-transparent rotating window, and at least one microwave inlet, at least one wet gas outlet, and at least one dry-end product outlet.    USE - The microwave-assisted flash pyrolysis system and method are useful for flash-pyrolyzing a feedstock (all claimed).    ADVANTAGE - The microwave-assisted flash pyrolysis system can effectively carry out microwave assisted flash pyrolysis in an industrial scale to reclaim matter or energy from waste or biomass.    DETAILED DESCRIPTION - A microwave-assisted flash pyrolysis system, comprises: at least one microwave generator connected to a chamber; where the chamber comprises: at least one feedstock inlet, at least one first baffle plate, a microwave-transparent rotating window, and at least one microwave inlet, at least one wet gas outlet, and at least one dry-end product outlet; where the feedstock inlet for introducing feedstocks to the microwave-transparent rotating window is disposed over the microwave-transparent rotating window and in front of the first baffle plate; where the first baffle plate is used for leveling out the feedstocks on the microwave-transparent rotating window and separating the chamber into different pyrolysis sectors in which flash pyrolysis is to take place; where the first baffle plate is disposed over the microwave-transparent rotating window, and there is a gap between the first baffle plate and microwave-transparent rotating window; where the height of the gap is adjustable and used for determining the thickness of input feedstocks; where the microwave-transparent rotating window moves the input feedstocks through the gap and into the pyrolysis sector; where the pyrolysis sector is disposed over the microwave inlet; where the microwave inlet is connected to the microwave generator for introducing microwave energy upward into the pyrolysis sector that is disposed over the microwave-transparent rotating window and limiting the microwave energy between the first baffle plate and the dry-end product outlet; where the wet gas outlet is connected to a gas collection unit for collecting wet gas from the pyrolysis sector, and the wet gas outlet is disposed over the microwave-transparent rotating window; where the dry-end product outlet is connected to the chamber for collecting pyrolyzed dry-end products from the microwave-transparent rotating window. An INDEPENDENT CLAIM is a method for flash-pyrolyzing a feedstock by using a microwave assisted pyrolysis system, comprising: introducing a feedstock through a feedstock inlet into a chamber; letting a microwave-transparent rotating window to move the feedstock through a gap into a pyrolysis sector; where the gap is disposed between the first baffle plate and microwave-transparent rotating window; pyrolyzing the feedstock by an upward direction of microwave energy through the microwave-transparent rotating window coming from a microwave inlet, where a wet pyrolysis gas and a pyrolyzed dry-end product will be produced by a flash pyrolysis process; collecting the wet pyrolysis gas by a gas collection unit through a wet gas outlet; and transporting the pyrolyzed dry-end product to a dry-end product outlet; where the pyrolyzed dry-end product is transported out of the chamber.