The invention provides a check valve assembly, a gas-lift valve, a gas-lift tool and an integrated string. The check valve assembly provided by the invention comprises a valve body, a one-way assembly and an end cap; a fluid in the valve body can only flow to a second end of a through hole from a first end of the through hole through arranging the one-way assembly in the through hole of the valve body, so that one-way flowing of the fluid is achieved; the compressive property of the check valve assembly is improved through arranging the end cap at the second end of the through hole in the valve body, and the gas-lift valve can still keep normal working in an acid fracturing transformation process at high pressure, so that the one-way assembly can be directly put into a well in the acid fracturing transformation process, and the string does not need to be replaced before gas-lift production, thereby completing acid fracturing transformation and gas-lift production through running the string, shortening the operation time and improving the work efficiency.