Objective To synthesize PEG-P[Asp(DET)] with 10% cholesterol chloroformate modified on its side chain and to study the physicochemical properties and cellular uptake of polymer complex PEG-P[Asp(DET)]-chole/hsa-miR-15a. Methods PEG-P[Asp(DET)] was synthesized by ring opening polymerization and modification with cholesterol chloroformate to acquire hydrophobicity, and MRI was used to verify its structure. The particle size, Zeta potential, stability, encapsulation efficiency, and cytotoxicity of the polymer complex PEG-P[Asp(DET)]-10% chole/hsa-miR-15a were examined. Finally, in vitro cellular uptake experiment was carried out with the leukemia cell line K562. Results The synthesized polymer PEG-P[Asp(DET)]-10% chole had fine solubility and could form into stable polymer complex PEG-P[Asp(DET)]-chole/hsa-miR-15a. When nitrogen-phosphorus ratio (N/P) was at 20 and concentration of the miRNA was 5 μmol/mL, the particle size was (192.4±10.8) nm, Zeta potencial was (6.9±0.9) mV, and encapsulation efficiency was (90.5±3.2)%. The complex displayed good stability under experimental condition. In vitro cellular uptake experimental indicated that the uptake capacity of PEG-P[Asp(DET)]-10%chole/hsa-miR-15a was higher than that of the commercial agent lipo2000. Conclusion PEG-P[Asp(DET)]-10%chole is a fine gene polymer carrier for miRNA and can achieve stable cellular uptake of miRNA.