A method of regenerating a field emission electron source, the electron source comprising at least one emission site fixed on a needle tip, the at least one emission site including a reaction product formed by metal atoms fixed on a surface of the tip and gas molecules under an electric field, the at least one emission site is rooted on the surface of the tip, rather than the gas molecules or dissociative particles that are dissociative on the surface of the tip, the method comprising: regenerating the electron source in situ in case that an emission capability of the electron source satisfies a regeneration condition, wherein the regeneration condition comprises: a current emission capability of the electron source drops below a first set threshold; regenerating the electron source in situ to re-form emission site, wherein re-formed emission site including a reaction product formed by metal atoms and gas molecules under the electric field, and the re-formed emission site being rooted in the surface of the tip, rather than dissociative on the surface of the tip; wherein the electric field is generated by applying one or more of a positive bias voltage and a negative bias voltage, a field strength of the electric field when the positive bias voltage is applied is less than the voltage value for field evaporation of the emission site and is ranging from 1 V/nm to 50 V/nm, and a field strength of the electric field when the negative bias voltage is applied is greater than the voltage value corresponding to a first emission current threshold of the electron source and is ranging from 1 V/nm to 30 V/nm; wherein a material of the metal atoms comprises any one or more of the following: tungsten, tantalum, niobium, molybdenum, rhenium, hafnium, iridium, osmium, rhodium, ruthenium, platinum, palladium, gold, chromium, vanadium, zirconium, titanium, and metal-hexaboride; wherein the gas molecules comprise hydrogen-containing gas molecules, or hydrogen-containing gas molecules and any one or more kinds of the following gas molecules: nitrogen-containing gas molecules, carbon-containing gas molecules, or oxygen-containing gas molecules; and wherein the emission site is formed by applying the electric field to the needle tip in a hydrogen-containing atmosphere within a first pressure range; wherein a temperature of the needle tip is lower than or equal to 1000K, and the first pressure range is lower than or equal to 1E -3 Pa; or the temperature of the needle tip is higher than or equal to 500K and lower than or equal to 800K, and the first pressure range is lower than or equal to 10 -6 Pa; or the temperature of the needle tip is lower than or equal to 150K, and the first pressure range is lower than or equal to 10 -6 Pa. regenerating the electron source in situ in case that an emission capability of the electron source satisfies a regeneration condition, wherein the regeneration condition comprises: a current emission capability of the electron source drops below a first set threshold; regenerating the electron source in situ to re-form emission site, wherein re-formed emission site including a reaction product formed by metal atoms and gas molecules under the electric field, and the re-formed emission site being rooted in the surface of the tip, rather than dissociative on the surface of the tip; wherein the electric field is generated by applying one or more of a positive bias voltage and a negative bias voltage, a field strength of the electric field when the positive bias voltage is applied is less than the voltage value for field evaporation of the emission site and is ranging from 1 V/nm to 50 V/nm, and a field strength of the electric field when the negative bias voltage is applied is greater than the voltage value corresponding to a first emission current threshold of the electron source and is ranging from 1 V/nm to 30 V/nm; wherein a material of the metal atoms comprises any one or more of the following: tungsten, tantalum, niobium, molybdenum, rhenium, hafnium, iridium, osmium, rhodium, ruthenium, platinum, palladium, gold, chromium, vanadium, zirconium, titanium, and metal-hexaboride; wherein the gas molecules comprise hydrogen-containing gas molecules, or hydrogen-containing gas molecules and any one or more kinds of the following gas molecules: nitrogen-containing gas molecules, carbon-containing gas molecules, or oxygen-containing gas molecules; and wherein the emission site is formed by applying the electric field to the needle tip in a hydrogen-containing atmosphere within a first pressure range; wherein a temperature of the needle tip is lower than or equal to 1000K, and the first pressure range is lower than or equal to 1E -3 Pa; or the temperature of the needle tip is higher than or equal to 500K and lower than or equal to 800K, and the first pressure range is lower than or equal to 10 -6 Pa; or the temperature of the needle tip is lower than or equal to 150K, and the first pressure range is lower than or equal to 10 -6 Pa.