Abstract: Although the modulus of elasticity is named after the British scientist Thomas Young (1773—1829) and is called Young's modulus, the discovery of the modulus of elasticity was not done by Thomas Young alone. As early as the end of the 17th century, Jacob Bernoulli (1655—1705) touched upon the elastic modulus when he studied the deflection line of the beam. Many peoples, such as Leonhard Euler(1707—1783), Giordano Riccati (1709—1790), Claude-Louis Navier(1785—1836), etc., played important roles in this process. This paper attempts to outline the discovery process of the modulus of elasticity and explore the internal logic of the concept of mechanics.