The p53, “Guardian of Genome,” is a special type of protein acting as a tumor suppressor and transcription factor for Mdm2. The interaction between p53-Mdm2 protein pathway forms a negative feedback network where p53 activates Mdm2 and Mdm2 deactivates p53 through ubiquitination. The interaction between p53-Mdm2 plays an important role in cancer progression. In this paper, ordinary differential equation (ODE) is derived based on mass action kinetics of the chemical reactions of the protein pathway under normal condition of DNA. A system model of p53-Mdm2 pathway is derived for normal cells using Michealis-Menten kinetics. The system model describing the dynamics of the pathway is simulated in MATLAB R2014a environment. © 2021, Springer Nature Singapore Pte Ltd.