A smart watch, comprising: a watch dial, a watch band, a monitoring apparatus and a mechanical transmission apparatus; wherein, a front surface and a rear surface of the watch dial are respectively set with sensors, and the sensors comprise: temperature sensors and optical sensors; the watch band is made of a hard material and has a multi-section structure; and beginning from a first section of the watch band fixedly connected to the watch dial, each section of the watch band is a hollow cavity structure that accommodates a next section of the watch band, to enable all other sections of the watch band except the first section of the watch band retract into previous sections of the watch band; wherein: the monitoring apparatus is set in the watch dial, and arranged to monitor temperature and light intensity of the sensors on the front surface and/or the rear surface of the watch dial and judge whether the temperature and light intensity reach preset thresholds; and the mechanical transmission apparatus is set between the watch dial and the watch band, and is arranged to, when both the temperature and the light intensity reach the preset thresholds, control other sections of the watch band except the first section of the watch band to extend or retract, to automatically remove and wear the watch band, wherein the mechanical transmission apparatus comprises: a motor and a gear set in the watch dial, and a plurality of rollers and belts set in the watch band, wherein, the belts are wrapped out of the plurality of rollers; the motor is arranged to drive the gear to rotate, and the gear drives the belts, to realize retraction of a plurality of sections of the watch band. a watch dial, a watch band, a monitoring apparatus and a mechanical transmission apparatus; wherein, a front surface and a rear surface of the watch dial are respectively set with sensors, and the sensors comprise: temperature sensors and optical sensors; the watch band is made of a hard material and has a multi-section structure; and beginning from a first section of the watch band fixedly connected to the watch dial, each section of the watch band is a hollow cavity structure that accommodates a next section of the watch band, to enable all other sections of the watch band except the first section of the watch band retract into previous sections of the watch band; wherein: the monitoring apparatus is set in the watch dial, and arranged to monitor temperature and light intensity of the sensors on the front surface and/or the rear surface of the watch dial and judge whether the temperature and light intensity reach preset thresholds; and the mechanical transmission apparatus is set between the watch dial and the watch band, and is arranged to, when both the temperature and the light intensity reach the preset thresholds, control other sections of the watch band except the first section of the watch band to extend or retract, to automatically remove and wear the watch band, the monitoring apparatus is set in the watch dial, and arranged to monitor temperature and light intensity of the sensors on the front surface and/or the rear surface of the watch dial and judge whether the temperature and light intensity reach preset thresholds; and the mechanical transmission apparatus is set between the watch dial and the watch band, and is arranged to, when both the temperature and the light intensity reach the preset thresholds, control other sections of the watch band except the first section of the watch band to extend or retract, to automatically remove and wear the watch band, wherein the mechanical transmission apparatus comprises: a motor and a gear set in the watch dial, and a plurality of rollers and belts set in the watch band, wherein, the belts are wrapped out of the plurality of rollers; the motor is arranged to drive the gear to rotate, and the gear drives the belts, to realize retraction of a plurality of sections of the watch band.