Background: Myeloid-derived suppressor cells (MDSCs) could prevent allograft rejections and induce immune tolerance in transplantation models. Previous studies demonstrated that inhibition of mTOR signal could enhance MDSCs protective effect in cardiac transplantation model via promoting MDSCs expansion. And the inhibition of mTOR is related with autophagy. Herein, this study was designed to investigate the protective mechanism of mTOR deficiency M-MDSCs in cardiac transplantation model. Methods: Myeloid-specific mTOR conditional knockout mice were generated to get mTOR deficiency M-MDSCs. The proliferation and immunosuppressive function of mTOR deficiency M-MDSCs were determined by flow cytometry and CFSE T cell proliferation assays. mTOR deficiency M-MDSCs intracellular autophagy levels were determined by western blot and Electron microscopy. RNAseq analysis was performed for WT and mTOR-deficient M-MDSC cells. Cervical cardiac transplantation model mice were generated. ELISA were performed for control mice, model mice, WT MDSCs infusion model mice and mTOR-deficient MDSCs infusion model mice to examine the inflammatory cytokines in the recipients mice serum. Flow cytometry and immunohistochemistry were performed to determine mTOR-deficient MDSCs induced immune tolerance. Results: mTOR deficiency could promote M-MDSCs differentiation and enhance intracellular autophagy levels in vivo and in vitro. mTOR deficiency also enhance the immunosuppressive function of M-MDSCs. In addition, infusing mTOR deficiency M-MDSCs could also prolong cardiac allograft survival and establish immune tolerance in recipient mice by inhibiting T cell activation and inducing Tregs. Conclusion: mTOR-deficiency enhances M-MDSCs cells autophagy and immunosuppressive function and prolongs mice cardiac allograft survival. Overall design: Wild-type (WT) and mTOR-deficient (KO) M-MDSC cells were induced from WT mice and Lyz-mTOR mice (n=3). Total RNA was isolated by Trizol (Sigma). RNA quality was determined by the ratios of A260/A280 using Nanodrop 2000 spectrophotometer (Thermo Fisher Scientific). RNAs were further tested using an Agilent 2100 Bioanalyzer (Agilent Technologies), and samples with RIN>7 were selected for sequencing library construction using the (Illumina). And the final library was sequenced on Illumina Novaseq 6000 sequencer. On average about 20 million 150bp paired end reads were generated per sample.