There is a lot of growth in Wi-Fi technology, that has given rise to Internet access without the need of wires. In IEEE 802.11 protocol, many vulnerabilities are present at the MAC layer which give rise to a lot of Denial of Service (DoS) attacks. In this manuscript we mainly concentrate on de-authentication DoS attack in Wi-Fi Networks. The victim station get disconnects from the network due to the de-authentication DoS attack. Minimum resources are required to launch the de-authentication attack. However, the schemes for detecting the de-authentication DoS attack suffer from major drawbacks namely, require protocol modification, require firmware upgradation, no proof of correctness etc. To acknowledge these issues, a Discrete Event System (DES) based Intrusion Detection System (IDS) for detection of de-authentication attack is proposed.