Usually,the mechanical properties of materials are measured by placing a small specimen in testing machines and following the standard procedure set by a recognized organization such as ASTM.Due to the length scale of nanomaterials,even some novel measuring techniques have been developed the accuracy and reliability of the testing results are still shrouded with uncertainty.To have a proper guidance on the mechanical properties of nanomaterials,a lot of efforts have been put on their prediction through theoretical and numerical simulation.Currently,most of the simulation methods are based upon molecular dynamics simulation,or finite element method,or others.Owing to the vast number of atoms involved in the simulation,it is usually very time consuming.To improve the computational process,recently a semi-analytical method called molecular-continuum model was proposed to estimate the stiffness,strength and fracture toughness of nanomaterials.This model was developed by combining the concept of molecular dynamics and continuum mechanics,in which the potential energy describing the interactions of atoms is not restricted to the harmonic potential function,and hence its deriving stress-strain relation is not restricted to be linear.The estimated properties can therefore be the ones defmed based upon the initial linear region such as stiffness,or the ones occur at the later period of the materials such as strength and toughness.By using this model,several mechanical properties ofnanomaterials such as Youngs modulus,Poissons ratio,shear modulus,ultimate strength,and fracture toughness have been estimated.For the purpose of illustration and verification,some examples of graphene,carbon nanotubes and single crystal cooper are presented in this paper.