A valve for automatically discharging cold water, comprising: a valve body provided with a first water inlet and a first water outlet; a first channel for discharging cold water, provided between the first water inlet and the first water outlet inside the valve body; a first valve assembly having a temperature sensing unit and a first plugging unit: a second channel for discharging mixed water, provided between the first water inlet and the first water outlet inside the valve body and connected in parallel with the first channel; a second valve assembly configured to open or close the second channel; wherein the first plugging unit is configured to open or close the first channel by means of heat expansion and cold contraction of the temperature sensing unit, wherein the first valve assembly further comprises a first chamber with an opening at one end thereof; the valve body is provided with a first annular water passing surface and the first annular water passing surface is provided with a first water passing hole communicated with the first water inlet; the first annular water passing surface is provided opposite to an opening of the first channel, and a gap always communicated with the first water outlet is formed between the first annular water passing surface and the opening of the first channel; the first plugging unit opens or closes the first channel by realizing or cutting off the communication between the first water passing hole and the gap, characterised in that the second valve assembly comprises a valve seat sealingly connected in the valve body and a second plugging unit; a water passing path is provided inside the valve seat, and is a part of the second channel; the second plugging unit is slidably provided to the valve seat to open or close the water passing path and further open or close the second channel, wherein the second plugging unit comprises a sliding rod, a second annular plug, a button and a second spring; the water passing path is provided with a step hole, and the second annular plug opens or closes the water passing path by realizing or cutting off the communication between a big hole and a small hole of the step hole; the sliding rod slides inside the step hole with one end being located in the big hole, and the other end passing through the small hole, extending out of the valve seat and being fixedly connected with the button; the second annular plug is fixedly connected to a part, which is located in the big hole, of the sliding rod, with the outer diameter being greater than the aperture of the small hole and less than the aperture of the big hole; the second spring is sleeved on the sliding rod and located between the valve seat and the button; under an initial state, the second annular plug presses against a step surface of the step hole and cuts off the communication between the big hole and the small hole; when the button is pressed, the sliding rod drives the second annular plug to be away from the step surface and realize the communication between the big hole and the small hole; when the button is released and the sliding rod and the second annular plug undergo a water pressure that is greater than or equal to a deformation force of the second spring, the water passing path is kept open; when the button is released and the sliding rod and the second annular plug undergo a water pressure that is less than the deformation force of the second spring, the second spring drives the sliding rod and the second annular plug to return to the initial state.