The invention discloses a test apparatus and a method for testing post-perforation interlayer isolation properties of a cement sheath. The test apparatus mainly comprises a simulation casing, simulation surrounding rock, a kettle, a heating sleeve, an internal pressure pump, a thermocouple, a flow meter and a computer. The method includes solidifying cement paste in an annular space between the simulation casing and the simulation surrounding rock and then filling the casing with oil or gas or water; applying pressures into the casing by the aid of the internal pressure pump; allowing the oil or the gas or the water to move along interfaces of the simulation casing and the cement sheath, a cement sheath body and interfaces of the cement sheath and the simulation surrounding rock to reach an end surface of the cement sheath if the cement sheath is damaged under the effect of internal pressures of the casing; measuring the magnitude of flow by the aid of the flow meter mounted on the end surface of the cement sheath; judging post-perforation interlayer isolation properties of the cement sheath. The test apparatus and method have the advantages that the test apparatus and the method are reliable in principle and easy and convenient to implement, the post-perforation oil, gas and water isolation properties of the cement sheath can be measured under different wellbore configuration simulation conditions, and technical support can be provided for safety production of oilfields in late periods.