Spill fire is a typical fire type that endangers industrial safety. This work systematically investigates the burning characteristics of transformer oil spill fire under different fuel leakage rates and substrate tilt angles, and the fuel flow hydrodynamic parameters. According to the flame spread behavior and substrate temperature distribution, the spill fire spread process is divided into four stages and the substrate is divided into three zones. The relative difference between max burning length and stable burning length is positively correlated with the substrate tilt angle. The increase of fuel flow velocity contributes to the flame spread velocity, but the increase of fuel flow velocity and the decrease of fuel layer thickness weaken the accelerating effect of surface flow on flame spread, which leads to a decreasing trend of flame spread velocity increase. The spill fire mass burning rate is 0.161–0.358 times of pool fire, and the increase of heat loss due to fuel flow and the radiant heat loss through the fuel layer dissipated through the substrate are the main reasons for the lower mass burning rate than pool fire. The research results provide basic data and references for further research on the formation mechanism of heavy oil spill fire and the prevention and control of small-scale spill fire.