The invention provides a natural fiber crystal variation modified liquid medium filling and recovery system based on paralleled multiple buses and multiple modified kettles. The natural fiber crystal variation modified liquid medium filling and recovery system based on the paralleled multiple buses and multiple modified kettles comprises a liquid medium low-pressure mass flow liquid-filling bus, a liquid medium high-pressure small flow liquid-filling bus, a liquid medium low-pressure mass flow liquid-return bus, a liquid medium low-pressure small flow liquid-filling bus, a gas phase balance bus, and n modified kettles which are in parallel connection on the buses, and n >=1. The invention further provides a natural fiber crystal variation modified liquid medium filling and recovery method based on the paralleled multiple buses and multiple modified kettles. The liquid-filling process comprises mass flow balance liquid filling and small flow pressure boosting liquid filling, and the liquid return process comprises mass flow pressure relief liquid return, mass flow balance liquid return, small flow balance liquid return, and cage shift liquid exhaustion. The natural fiber crystal variation modified liquid medium filling and recovery system and the method based on paralleled multiple buses and multiple modified kettles are good in modified effect, small in system energy consumption, and high in production efficiency.