At the end of a power transmission line, the cable should be terminated carefully, otherwise it will create problems during the operation. A special equipment called termination is designed to tackle down the problems from cable ends. The main functional part of a termination is a piece of rubber with a cone shape. This rubber cone has a semi-conductive layer which is connected with ground potential. By doing this, the cone smoothens the concentric equipotential lines at the cable end, so the electric field stress there can be decreased. The cone in the termination is called stress cone. However, insulation degradation on the termination stress cone due to water contamination is often found in its operation. This, in the end, will cause operation failures in the power network. This research aims to investigate the influences brought by water contamination on the stress cone, and discuss possibilities of detecting the presence of water content by using electrical methods. By using 3D FEM simulations, the changes of electric field distribution, especially the filed along the oil-rubber interface, were studied. Based on the simulation results, we built up a small scale test setup to observe how water contamination behaves on the oil-rubber interface, and measured the changes of partial discharge signals and tanδ values. As conclusions, we discussed the electrical ways of detecting the presence of water contamination on the stress cone, and gave suggestions for the future work.