The invention discloses a water leakage detection device used for a high voltage converter and a combined device thereof. One end of a water-sensitive member is connected with the sidewall of the left side of a shell, and the other end is connected with a light shading slide block. The light shading slide block is also connected with the left end of an elastic member. The right end of the elastic member is connected with the sidewall of the right side of the shell. A light signal transmitting end is installed on the front sidewall of the shell or installed on the rear sidewall of the shell. A light signal receiving end is installed on the opposite sidewall of a light signal transmitter. Light shading and sensitive material is immersed in the water and then the tensile strength is reduced and the material can be pulled apart by the elastic member so that the light shading slide block is enabled to move to the right side of the shell under the pulling effect of the elastic member. When the pulling force of the elastic member and the resistance of the light shading slide block are balanced, the light shading slide block stops moving and can shade light signal transmission between the light signal transmitting end and the light signal receiving end. The invention also discloses the water leakage detection combined device used for the high voltage converter and a method thereof. The water leakage detection device is convenient to install and maintain so that the water leakage situation of the high voltage converter can be accurately detected.