Optimisation of mine goaf gas drainage design needs to fully recognise mine geological conditions, mining induced caving characteristics and gas flow dynamics. This paper presents the integrated geotechnical and gas field studies carried out at the Blakefield South mine for optimisation of longwall goaf gas drainage. A set of instruments including extensometers, piezometers, gas pressure gauges, tracer gases and borehole cameras were adopted in these studies. The overburden strata caving processes, coal seam pore pressure changes, multi-seam gas flow paths, goaf gas pressure dynamics, and drainage borehole stability were observed. The studies enabled a clear identification of the extent and characteristics of mining influence, sources of gas emissions in both the roof and floor and goaf gas flow dynamics, and have led to a successful design and implementation of an optimal goaf gas drainage system at the Blakefield South mine.