A valve stem and valve core assembly and a valve including a valve stem and valve core assembly. The valve stem and valve core assembly includes a valve stem and a valve core that sleeves the valve stem. The assembly includes an adjusting device arranged on the valve stem, and an elastic element arranged between the adjusting device and the valve core. A clearance exists between the valve core, the valve stem, and the adjusting device, so that the valve core can move relative to the valve stem, such that the valve can have a good closing performance.