A fully modularized, bottom-feed type pyrolysis reactor includes a reactor vessel, a feeding unit, an integrated grate, and an ash/char discharge unit. The reactor vessel includes detachable upper and lower vessels. The integrated grate is rotatable and integrated to an air inlet unit, feeding unit, and discharge unit. A water-cooled cooling and stirring pipe is mounted on a top face of the integrated grate, and an ash/char discharge unit is located at the bottom of the integrated grate. Ash/char is discharged through discharge gate unit, addressing the problems of inconvenient transportation, installation of the pyrolysis reactor, and imprecise temperature control. Manufactured in a modular fashion, the electrical and monitoring systems are pre-assembled and comprehensively tested before transportation to the site, reducing installation time by 90% while ensuring installation quality and allowing for various orientation configurations to meet customers' on-site requirements without altering the overall design of the reactor.