Objective To investigate the expression and relationship between miR-145-5p and multidrug resistance gene (MDR1) protein P-glycoprotein(P-gp) in colorectal cancer.  Methods SP, Real-time PCR and Western blotting were used to detect the expression of P-gp colorectal carcinoma (CRC) in 50 patients and in 30 paracancerous normal tissue patients, the effect of miR-145-5p expression on MDR1 mRNA and P-gp and the correlation between them and clinicopathological features.   Results The expression level of miR-145-5p in CRC was significantly lower than that in paracancerous normal tissue, and the expression level of MDR1 mRNA and P-gp was significantly higher than that in paracancerous normal tissue (r=-0.403, P<0.01).MiR-145-5p could inhibit the expression of MDR1 mRNA and P-gp in HCT-15 cells(P<0.05).   Conclusion MiR-145-5p plays a regulatory role in the expression of multidrug resistance genes and proteins in colorectal cancer, and is involved in the occurrence, development and multidrug resistance of colorectal cancer.