HRD1 and DOA10 complexes are two major components involved in the endoplasmic reticulum-associated protein degradation (ERAD) system in eukaryotic organisms. However, the relationship between these two complexes is largely unknown, especially in higher eukaryotes. Our previous work has shown that UBC32, an ERAD component in Arabidopsis, is regulated by HRD1 complex which is an ERAD tuning activity conserved in eukaryotes. That is a regulation of the HRD1 complex to the essential component in the DOA10 complex and here, we report a reverse ERAD tuning example in plants. In this work, our results showed that UBC32 interacts in vivo and in vitro with AtOS9, a component of HRD1 complex. AtOS9 itself is regulated by 26S proteasome. Furthermore, compared with WT, we found AtOS9 is accumulated in ubc32 mutants and the E2 activity of UBC32 is essential to the degradation of AtOS9. In addition, atos9 could rescue the Tm and NaCl sensitive phenotype conferred by ubc32. Taken together, we showed UBC32 negatively regulated the stability of AtOS9, which is another ERAD tuning activity in plant.