An ultraviolet lamp includes a lamp tube and an electrode. A discharge cavity is formed in the lamp tube. A thermistor is disposed on an end socket at a first end of the lamp tube. A receiving groove communicated with the discharge cavity is formed in the end socket and contains amalgam. The thermistor heats the amalgam in the receiving groove in the end socket. The Curie temperature of the thermistor ranges from [T1+(T2−T1)/5] to [T1+4*(T2−T1)/5], wherein T1 and T2 are respectively a minimum operating temperature and a maximum operating temperature of the amalgam in a continuous region where the ultraviolet radiation power is from 90% to 100% when the input power of the ultraviolet lamp is 100%.