The present invention discloses an optical switch (100), including a first optical waveguide (121), a second optical waveguide (122), and a first heater (110), where a place at which a distance between the first optical waveguide (121) and the second optical waveguide (122) is the smallest is a junction, the first optical waveguide (121) includes a first optical sub-waveguide (1211) and a third optical sub-waveguide (1212), and the second optical waveguide (122) includes a second optical sub-waveguide (1221) and a fourth optical sub-waveguide (1222); the first heater (110) is adjacent to the third optical sub-waveguide (1212); and there is a first dielectric material (140) between the first heater (110) and the third optical sub-waveguide (1212), and there is a second dielectric material (141) between the third optical sub-waveguide (1212) and the fourth optical sub-waveguide (1222), where a thermal conductivity of the first dielectric material (140) is greater than a thermal conductivity of the second dielectric material (141). The optical switch (100) in the present invention has advantages such as high heating efficiency, a small quantity of heaters, and simple control.