Thin films play an important role in many technological applications including microelectronic devices, magnetic storage media, MEMS and surface coatings. It is well known that a thin film’s material properties can be very different from the corresponding bulk properties and thus there has been a strong need for the development of a miniature tester to measure the mechanical properties of a thin film. Two testers are designed and set up in small size of 62 ㎜ width, 20 ㎜ depth and 90-120 ㎜ height to fit in a chamber of scanning electron microscope (SEM). One tester has a homemade 0.2 N load cell and a low-priced electromagnetic actuator. The other has a commercial 5 N load cell, a 52 ㎛ piezoelectric actuator and some novel grips. Two types of 3.5 microns thick polysilicon specimen are tested to prove the testers’ applicability. The strain is measured by the two ways. Firstly, it is measured by an ISDG system in the atmosphere for the reference. Secondly, the same test is repeated in a SEM chamber to monitor the strain as an in-situ experiment. The strain is evaluated by observing the gap change between two markers.