The energy and environmental problems brought by petrochemical products promote the development of green and sustainable materials. Natural fiber reinforced plant-derived polylactic acid (PLA) is an attractive sustainable strategy. However, the lack of functionality largely limits its wider application. In this study, the most promising bamboo fiber (BF) whose versatility was realized by electroless plating (ELP) was selected as the reinforcing phase. By filling metallized BF(MBF) into PLA and then treating it by hot pressing, a low-cost, multifunctional MBF/PLA biomass composite(MBPC) was prepared. Results show that the ELP treatment of BF can not only significantly improve the thermal stability and mechanical properties of the composites but also endow it with excellent electromagnetic shielding, electro-thermal and photo-thermal conversion capabilities. Thereinto, the 70 wt%-MBPC has an electrical conductivity of 20.86 S/cm and an SE value of 45 dB in the X-band. The greater concern is the amazing electrothermal conversion performance, which can be heated rapidly at low voltage. Under the voltage of 3V, the temperature reaches 160 °C in about 50s. Besides, MBPC also possesses solar-driven heating, which can be rapidly heated to 75 °C under irradiation within 240s. This green and low-cost biomass multifunctional composite is expected to be used for electromagnetic shielding, energy conversion, and smart furniture, etc.