An explosion-proof sheet for a secondary battery, wherein the secondary battery comprises a top cover which is provided with an explosion-proof hole; the explosion-proof sheet is assembled on the top cover to close the explosion-proof hole; wherein the explosion-proof sheet comprises: a main body portion which is opposite to the explosion-proof hole, wherein a strengthening region being formed on the main body portion; a fixing portion which is arranged around the main body portion to be connected to a periphery of the explosion-proof hole; and a cracking portion which is located between the fixing portion and the main body portion and is connected to the fixing portion and the main body portion; wherein in a thickness direction of the explosion-proof sheet, a thickness of the main body portion at other positions except for the strengthening region is h1; a thickness of the main body portion at the strengthening region is h2; and a thickness of the cracking portion is h3, wherein h1 > h2 and h1 > h3; or wherein h1 ≥ 2h2, h2 ≥ h3; wherein the strengthening region is formed on the main body portion in a squeezed manner, and the strengthening region forms a groove on the main body portion, wherein the grooved is sunken relative to an upper surface of the main body portion, and wherein a material density of the main body portion at the strengthening region is greater than a material density of the main body portion at other positions; wherein the explosion-proof sheet further comprises a connection portion which is located between the fixing portion and the main body portion and is connected to the fixing portion and the main body portion; the connection portion is connected to an end part of the cracking portion; a thickness of the connection portion is h4; a thickness of the cracking portion is h3; and the thickness of the main body portion at other positions is h1, wherein h1> h4 > h3; characterized in that a plurality of cracking portions and a plurality of connection portions are provided; the plurality of cracking portions are disposed at an interval; the plurality of connection portions are respectively connected between the plurality of cracking portions; wherein a thickness of at least one connection portion is less than a thicknesses of other connection portions; wherein each thickness of the plurality of cracking portions satisfies h1 > h3 when h1 > h2, or h2 ≥ h3 when h1 ≥ 2h2; and each thickness of the plurality of cracking portions and each thickness of the plurality of connection portions satisfy h1 > h4 > h3 and wherein the strengthening region has a first end and a second end; the first end and the second end extend to a joint of the connection portion and the cracking portion. a main body portion which is opposite to the explosion-proof hole, wherein a strengthening region being formed on the main body portion; a fixing portion which is arranged around the main body portion to be connected to a periphery of the explosion-proof hole; and a cracking portion which is located between the fixing portion and the main body portion and is connected to the fixing portion and the main body portion; wherein in a thickness direction of the explosion-proof sheet, a thickness of the main body portion at other positions except for the strengthening region is h1; a thickness of the main body portion at the strengthening region is h2; and a thickness of the cracking portion is h3, wherein h1 > h2 and h1 > h3; or wherein h1 ≥ 2h2, h2 ≥ h3; wherein the strengthening region is formed on the main body portion in a squeezed manner, and the strengthening region forms a groove on the main body portion, wherein the grooved is sunken relative to an upper surface of the main body portion, and wherein a material density of the main body portion at the strengthening region is greater than a material density of the main body portion at other positions; wherein the explosion-proof sheet further comprises a connection portion which is located between the fixing portion and the main body portion and is connected to the fixing portion and the main body portion; the connection portion is connected to an end part of the cracking portion; a thickness of the connection portion is h4; a thickness of the cracking portion is h3; and the thickness of the main body portion at other positions is h1, wherein h1> h4 > h3; characterized in that a plurality of cracking portions and a plurality of connection portions are provided; the plurality of cracking portions are disposed at an interval; the plurality of connection portions are respectively connected between the plurality of cracking portions; wherein a thickness of at least one connection portion is less than a thicknesses of other connection portions; wherein each thickness of the plurality of cracking portions satisfies h1 > h3 when h1 > h2, or h2 ≥ h3 when h1 ≥ 2h2; and each thickness of the plurality of cracking portions and each thickness of the plurality of connection portions satisfy h1 > h4 > h3 and wherein the strengthening region has a first end and a second end; the first end and the second end extend to a joint of the connection portion and the cracking portion.