A lamp comprising: a support body; a lamp body; and at least an automatic mounting device arranged to detachably mount said lamp body on said support body, wherein two said automatic mounting devices are arranged on said support body in a symmetrical manner, wherein each of said automatic mounting devices is detachably mounted on said lamp body so as to allow said lamp body to be detachably mounted on said support body, wherein said lamp body has two mounting channels, wherein each of said automatic mounting devices comprises a mounting mechanism, a communication channel having a holding space and communicating the external environment with said holding space, a mounting base, a holding shell, and an elastic restoration mechanism, wherein said mounting mechanism comprises a mounting element which extends from said holding space to the external environment in a movable manner through said communication channel, wherein said mounting element of said automatic mounting device is adapted to automatically return to an installation state after passing through said mounting channel of said lamp body, so as for mounting said lamp body on said support body, wherein said mounting base is mounted on said holding shell, wherein said holding space is formed and defined between said mounting base and said holding shell, wherein said holding shell has said communicating channel arranged thereon, wherein said elastic resetting mechanism is kept between said mounting base and said mounting element, wherein said holding shell is arranged on said support body, wherein said holding shell is arranged on said support body in a manner that said holding shell is mounted on said support body; or said holding shell is arranged on said support body in a manner that said holding shell is integrally formed on said support body, characterized in that said mounting element has a holding groove, a bulge structure for defining a retention slot, and a guide surface, wherein a part of said lamp body is adapted to be held in said holding groove of said mounting element, wherein a groove bottom of said holding groove is an inclined surface, wherein said bulge structure is located at a low end of said retention slot. a support body; a lamp body; and at least an automatic mounting device arranged to detachably mount said lamp body on said support body, wherein two said automatic mounting devices are arranged on said support body in a symmetrical manner, wherein each of said automatic mounting devices is detachably mounted on said lamp body so as to allow said lamp body to be detachably mounted on said support body, wherein said lamp body has two mounting channels, wherein each of said automatic mounting devices comprises a mounting mechanism, a communication channel having a holding space and communicating the external environment with said holding space, a mounting base, a holding shell, and an elastic restoration mechanism, wherein said mounting mechanism comprises a mounting element which extends from said holding space to the external environment in a movable manner through said communication channel, wherein said mounting element of said automatic mounting device is adapted to automatically return to an installation state after passing through said mounting channel of said lamp body, so as for mounting said lamp body on said support body, wherein said mounting base is mounted on said holding shell, wherein said holding space is formed and defined between said mounting base and said holding shell, wherein said holding shell has said communicating channel arranged thereon, wherein said elastic resetting mechanism is kept between said mounting base and said mounting element, wherein said holding shell is arranged on said support body, wherein said holding shell is arranged on said support body in a manner that said holding shell is mounted on said support body; or said holding shell is arranged on said support body in a manner that said holding shell is integrally formed on said support body, characterized in that said mounting element has a holding groove, a bulge structure for defining a retention slot, and a guide surface, wherein a part of said lamp body is adapted to be held in said holding groove of said mounting element, wherein a groove bottom of said holding groove is an inclined surface, wherein said bulge structure is located at a low end of said retention slot.