Abstract: Rubber is generally regarded as incompressible, isotropic, and hyperelastic material whose constitutive model is usually described in terms of strain energy density functions. An improved Yeoh model for hyperelastic material is proposed in this paper to improve the ‘soft’ property of the Yeoh model. The strain-stress relations of three special deformation modes for the proposed model are presented based on the large deformation theory of continuum mechanics, and compared with those obtained by the original Yeoh model and by the experiment data. It is found that:the improved Yeoh model represents an inversed "S" shape of the strain-stress relation, and effectively overcomes the ‘soft’ property of Yeoh model when predicting the strain-stress curve of equibiaxial extension at the same time. The proposed model precisely predicts the strain-stress relations of uniaxial, planar and equibiaxial tension-compression in a large strain range and has great values in engineering application.