This paper focuses on the problems of thermodynamic modeling and sensitivity analysis of the ejector in refrigeration. Firstly, a new thermodynamic model is proposed based on the assumptions of constant pressure mixing and constant area mixing. The proposed model contains fewer parameters and simpler structure compared with the traditional ejector models. Later, the sensitivity analysis of the ejector is carried out based on the adjoint sensitivity method. Three different sensitivity coefficients are given to reveal the relation between design parameters and ejector performance. The result shows that geometric parameters have the most influences on the entrainment ratio of the ejector. For the ejector using R600a, the sensitivity coefficients of entrainment ratio to A(t) and A(m) are -2.43% and 2.40% respectively. (C) 2018 Elsevier Ltd. All rights reserved.