Objective: To investigate the effects of different expression of monoacylglycerol lipase (MAGL) in tumor-associated macrophages (TAMs) with the proliferation of MHCC97H human liver cancer cells in vivo and its mechanism. Methods: Human peripheral blood-derived monocyte was induced to differentiate into M2-type TAMs and was identified by flow cytometry. The co-culture model of TAMs and MHCC97H human liver cancer cells was established, and the expression of MAGL in TAMs cells was detected by qRT-PCR. The expression of MAGL in TAMs cells was detected by plasmid transfection. ELISA and qRT-PCR was used to detect the mRNA expression levels and secretion levels of inflammatory factors in TAMs cells. The subcutaneous tumor model of MHCC97H mice was constructed to observe the effect of different expression of MAGL in TAMs cells with the proliferation of MHCC97H human liver cancer cells in vivo. F-test was used for the measurement of homogeneity of variance between two independent samples. A t-test was used for homogeneity of variance, and the corrected t-test was used for non-homogeneity of variance. Results: Human peripheral blood-derived monocytes were successfully induced to differentiate into M2-type TAMs. An in vitro co-culture model was established. qRT-PCR showed that MHCC97H human liver cancer cells significantly down-regulated the expressional level of MAGL in TAMs cells. The constructed subcutaneous tumor model of mice demonstrated that up-regulation up-regulation of MAGL expression in M2-type TAMs inhibited the proliferation of MHCC97H human liver cancer cells in vivo. Furthermore, the mechanistic study illustrated that the high expression of MAGL promoted the transcription and secretion of inflammatory factors such as interleukin-1 beta, interleukin-6 and tumor necrosis factor-alpha in M2-type TAMs cells. Conclusion The overexpression of MAGL inhibits the proliferation of MHCC97H hepatocellular carcinoma cells in vivo, and its mechanism may be associated to the release of inflammatory factors that from TAMs cells.