Abstract: Objective: To investigate the effect of long non-coding RNA RP11-85G21.1(lnc85) on the proliferation of hepatoma cells and its possible mechanism. Methods: The whole transcriptome RNA sequencing combined with reverse transcription-quantitative PCR(RT-qPCR) was used to screen and verify lnc85 with differentially high expression in liver cancer. The lnc85 overexpressing liver cancer cell line(OE) and control cells(control) were constructed by infecting cells with lnc85 overexpression/empty vector lentivirus. The interacting proteins of lnc85 were screened by RNA pull-down assay combined with mass spectrometry and verified by western blotting. MTT assay and cell clone formation assay were used to analyze the effect of cell proliferation after lnc85 overexpression. Bioinformatics analysis was used to analyze the expression level of lnc85 interacting protein and its effect on survival of patients with liver cancer. Results: The results of the whole transcriptome RNA sequencing showed that lnc85 was significantly highly expressed in the plasma exosomes of patients with liver cancer compared with the control group(P<0.001), and RT-qPCR verified that lnc85 was significantly increased in the three hepatoma cells(P<0.01, P<0.001). RNA pull-down combined with mass spectrometry showed that cell division cycle 42(CDC42) was an interacting protein of lnc85, and RT-qPCR confirmed that CDC42 level was significantly increased in hepatoma cells(P<0.001). In hepatoma cells with lnc85 overexpression, CDC42protein level was significantly up-regulated(P<0.001) and cell proliferation ability was significantly enhanced(P<0.01). Bioinformatics analysis showed that the expression level of CDC42 in patients with liver cancer was significantly higher than that in healthy controls(P<0.001), and the expressing level of CDC42 showed an increasing trend as the increase of tumor grade. High CDC42 expression was associated with poor prognosis in patients with liver cancer(P<0.001). Conclusion: The lnc85 is highly expressed in liver cancer and may promote the proliferation of hepatoma cells by targeting and regulating CDC42 expression.