In-situ tensile testing in TEM (transmission electron microscopy) is a useful tool for studying mechanical properties of nano-structures because it can provide quantitative information on sample deformation at atomic scale. This paper reports an in-situ tensile testing on a 90 nm-thick <110> SCS nanobeam in TEM JOEL 2010 by using a self-made TEM holder and an MEMS tensile-testing chip. A suspended SCS nanobeam, a comb drive actuator, a force sensor beam, and an electron beam window were integrated into the chip, which is fabricated by means of Si bulk micromachining and wafer bonding techniques. The in-situ tensile tests on the 90 nm-thick SCS nanobeam demonstrated its strain-stress relationship, and indicated that the Youngpsilas modulus as 167 Gpa, which doesnpsilat present obvious size effect.