Objective: To evaluate ampicillin to predict activity of Enterococcus faecalis and Enterococcus faecium to imipenem. Methods: A total of 127 non-duplicated strains of Enterococcus faecalis and 124 strains of Enterococcus faecium were collected from 23 hospitals in China. The antimicrobial susceptibility testing was determinated using broth microdilution and disk diffusion. Results: For all E. faecalis , when using penicillin/ampicillin results to predict susceptibility to imipenem (called as penicillin-imipenem prediction mode and amipicillin-imipenem mode), the categorical agreement (CA) and major error (ME) rate was 88.9%/95.3% and 6.3%/0%, whereas it was 89.7%/96.8% and 8.7%/1.6%, when using that results of disk diffusion, respectively. No very major error (VME) rate was founded for both prediction modes. For penicillin susceptible, ampicillin susceptible E. faecalis , the CA rate of ampicillin-imipenem prediction mode based on results from broth microdilution and disk diffusion to was both 100%, and neither was founded with VME or ME rate. For penicillin resistant, ampicillin susceptible E. faecalis , the CA rate of ampicillin-imipenem prediction mode based on results from broth microdilution and disk diffusion was 57.1% and 81.8%, respectively. And neither was founded with VME or ME rate. For penicillin resistant, ampicillin resistant E. faecalis , the CA/ME/VME rate of ampicillin-imipenem prediction mode based on results from broth microdilution and disk diffusion was 100%/0%/0% and 77.8%/22.2%/0%, respectively. For all E. faecium , the CA rate of penicillin-imipenem and ampicillin-imipenem prediction mode based on results from broth microdilution was 100% and 99.2%, and it was both 99.2% based on results from disk diffusion. ME and VME rate for all four prediction modes was 0%. For penicillin resistant, ampicillin resistant E. faecium , the CA rate was 100%, as well as penicillin susceptible, ampicillin susceptible E. faecium . None of prediction mode was found with ME or VME rate. Conclusion: For penicillin susceptible, ampicillin susceptible or penicillin resistant, ampicillin resistant E. faecalis and E. faecium , ampicillin susceptibility results of broth microdilution could accurately predict in vitro activity of imipenem. However, for penicillin resistant, ampicillin susceptible E. faecalis and E. faecium , using ampicillin results to predict imipemem susceptibility of was poorly consistent.