Abstract: Heavy metals and antibiotics were two kinds of general environmental pollutants, their effects on microorganism worth more attentions. In previous researches, 7 strains were isolated from wastewater of some intensive pig farms in Guangdong Province, which were of the co-resistance to heavy metal and antibiotics. One of them referred to as MA1, which was a gram negative bacilli, was studied on its cross-resistance to five heavy metals (Pb²⁺ , Cr⁶⁺ , Hg²⁺ , Cu²⁺ , Zn²⁺ ) and amoxicillin by the methods of minimum dichotomy and Kirby-bauer disk diffusion according to the inhibition zones diameter. Strain MA1 could be tolerated to Pb²⁺ of 100 mg/L, Cu²⁺ of 100 mg/L, Zn²⁺ of 100 mg/L, Cr⁶⁺ of 50 mg/L and Hg²⁺ of 10 mg/L, respectively, and it had specific resistance to amoxicillin. Although Hg²⁺ had the strongest antibacterial capability among the five heavy metal ions, when it coexisted with amoxicillin, Hg²⁺ of over 5 mg/L could increase the resistance of strain MA1 to amoxicillin greatly. The sensitivity of strain MA1 to amoxicillin increased with the concentration of all the others heavy metal ions, while the synergistic bactericidal capacity of Cr⁶⁺ decreased, though Cr⁶⁺ was obvious antimicrobial effect. Cu and Zn, which were generally considered to stimulate bio-resistance to heavy metal most likely, showed stronger bactericidal capability when coexisted with amoxicillin. The coexistence of heavy metal did have changed the sensitivity of strain MA1 on amoxicillin.