Security is a vital concern around the world and it has been major thread for all confidential departments. This work is based on Arduino and is used for the security purpose. Arduino is an open-source prototyping platform based on easy-to-use hardware and software. Arduino uses an ATmega2560 microcontroller. As security is essential nowadays, so by using this project only the authorized person will be allowed to enter by entering the correct password. It is very simple, cost effecting and secure. The lock can be open if the password entered is correct and matches the password which is already stored in the internal memory. It also consists of a LCD display which is used to interface with the project to output lock status. This project can be used in ATMs, doors of houses, lockers, offices and anywhere where security is needed. As a result of completing this project we wish to design and implement a coded lock system based on Arduino Microcontroller by designing a security systemfor the purpose of solving the general problem of locking security and making a system that can help to avoid the duplication and loss of keys.