This paper presents report of a design work on petroleum leakage detection system.It is a system that is designed to monitor seepage of petroleum products across pipeline installations.The design work which was simulated on a PROTEUS software,consists of a gas detecting sensor(GH-312),an 8-bit(AT89C51)Microcontroller,an alarm system and a remote PC.It was implemented as a laboratory prototype to sense seepages,generate an alarm and also send an alert message to a PC at remote location.Testing of the prototype was carried out in the laboratory using methane gas which is a component gas contained in petroleum products.Result shows an actuated alarm(upon the release of gas from test tube)and an instant alert message on the PC.