The effects of nano-carbon addition on soil enzyme activity，soil available nutrients，and tomato yield and quality were studied. The experiment was conducted in a greenhouse in Shijiazhuang，Hebei province，with four fertilization treatments: chemical fertilizer(CK)，chemical fertilizer + water(CKH)，chemical fertilizer + 0.1% nano-carbon (C1)， chemical fertilizer + 0.3% nano-carbon(C2). The effects of nano-carbon on enzyme activities related to soil carbon and nitrogen conversion，nitrate nitrogen，available potassium，and tomato yield and quality were investigated. The results showed that:(1)Application of nano-carbon significantly increased the activities of soil β-1，4-glucosidase， β-cellulosidase，β-1，4-N-acetylglucosaminidase，and leucine aminopeptidase.(2)Application of nano-carbon improved the soil nitrate nitrogen and available potassium content. During the peak harvesting period，soil nitrate nitrogen content increased by 50.7% and 122.8% in C1 and C2 treatment compared with CK，and by 46.1% and 115.9% compared with CKH， respectively. At harvest，soil available potassium content was 32.0% and 35.1% higher under C1 treatment than those of CK and CKH，52.4% and 55.9% higher under C2 treatment than CK and CKH，and 15.4% higher under C2 than C1 treatment. (3)The application of different amounts of nano-carbon showed the effect of increasing yield and improving the values of some tomato quality indexes. The addition of appropriate amount of nano-carbon to fertilizer could improve the activity of enzymes related to soil carbon and nitrogen conversion，improve the utilization and conversion of carbon and nitrogen in soil， and increase the content of nitrate nitrogen and available potassium in soil，which had the potential to increase the yield and improve the quality of tomato.