https://www.makeuseof.com/create-antivirus-software/

If you want to make an antivirus program, with little knowledge on how to do so, download a project from sourceforge, read the source code, & get evolved with the project. Machine level language are preffered to write antivirus - Generally VC++ Language is good choice.

Antivirus Sample Application

http://msdn.microsoft.com/en-us/library/bb204055(v=exchg.140).aspx

Microsoft Antivirus API

http://users.telenet.be/ws36637/msoav.html

Security Pilot Anti-Virus Devloping

http://securitypilotav.codeplex.com/

Super Av Anti Virus

http://superav.codeplex.com/

Super Av AntiVirus is an open source anti virus with full source code

Anyway, learn a software development language, I recommend C++. There are many components to an anti-virus, such as the engine, detection (signature vs heuristic), self defense, firewall, etc.

Start first with simple applications. These anti-virus companies invest hundreds of thousands of dollars into the development and maintaining of their products, hiring hundreds of programmers to do different tasks.