The invention relates to a current sensor, a coil packaging method thereof and an electronic current transformer. The current sensor comprises a coil and a sensor shell, wherein the coil and the sensor shell are coaxially arranged and provided with a spacing therebetween, the spacing is internally provided with a coil support, and the coil support is a foaming filler. The coil packaging method of the current sensor comprises a step of placing the coil into the sensor shell and enabling the coil and the sensor shell to be coaxially arranged, and further comprises a step of injecting a foaming material in a fluid form into the spacing between the coil and the sensor shell and enabling the foaming material to generate a curing reaction to fill the spacing and form the foaming filler in the spacing. The sensor is convenient to manufacture, simple in process, short in curing time, low in cost and light in mass. Meanwhile, the foaming filler is low in hardness, thereby being capable of avoiding damages for the coil, and improving the qualified rate of products.