The performance of Vacuum Insulation Panel (VIP) is always characterized by a vital parameter, that is, thermal conductivity. The precise measurement of thermal conductivity provides excellent quality assurance for VIP application. But the VIP in service, especially embedded in thermal envelopes, always cannot be evaluated by normal device. In this paper, a double hemispheres chambers device, based on thermal protection method, is proposed to measure the thermal conductivity of VIP in use. The device is portable and can be employed to measure VIP in various sizes. What is more, the device can also be used to evaluate VIP aging extent. The Experiments were carried out to prove the accuracy and the influencing factors were also analyzed. The results implied that the developed device had good precision and practicability. This method can be operated on spot and was not limited by the size of insulation materials, which overcomes the shortcomings of common testing techniques. The test results of the device have high credibility and small measurement error. Therefore, this device can be widely used for field testing and aging degree determination of VIP samples. The method and device proposed in this paper can achieve excellent performance and was more practical than the well-known ones.