Abstract: Inordertostudytheeffectofplasticfilmmulchingdealtwithdifferentwayonmungbeanyield,theauthor chose the cloudless fine weather to measure the photosynthetic indexes in the seed filling period of mung bean, and measured the phenotypic traits relating to mung bean yield in the mature period. The results showed that the plastic film mulching could increase soil temperature, retain moisture, keep nutrient, and increase photosynthetic efficiency, the mung bean had higher green degree, net photosynthetic rate, and its chorophyll content was significantly higher than no-covered (contrast), so its photosynthetic matter accumulation time was long, the yield had obviously increased. The mung bean yield was 2691 kg/hm2 with 140 cm water-osmosis plastic membrane covered, which increased by 20.9% to no-covered and 6.3% to narrow membrane treatment.