Understanding spatial distribution of particles in lung airways can be helpful in the field of targeted lung drug delivery research. Since mice are usually used in Pharmaceutical and toxicological tests of the respiratory system, achieving a CF-PD model of particle deposition in the mouse lung can be helpful to investigate the effects of various parameters on particle deposition in the mouse lung by creating a Repeatable model. In this research, the effect of gravity direction on particle deposition in the left lung airways of a mouse was investigated. High-resolution LSFM images were used to form the geometry. The obtained geometry was divided into different orders, and by modeling a laminar airflow rate of 72 ml⁄min and injecting particles with sizes between 1 µm and 10 µm into it, the effect of six different gravity directions on the amount of particle deposition at different orders was studied. The results of the study include the percentage of particles deposition in each order, the normal dose of particles in each order, and the average percentage and normal dose of particles in each order of the airways. According to the obtained results, the direction of gravity played an effective role in the rate of micro-particle deposition in the airways of the mouse lungs. The greatest effect of the gravity direction at a given particle size and order belongs to 2 µm particles in the third order of the airways, which showed a 2100% difference in the rate of deposition in the gravitational direction of -x and +z. The least effect of gravity direction on particle deposition is related to particle size of 3 µm and second order of the airways, where the difference between maximum particle deposition in the -y gravitational direction and its minimum value in the +y gravitational direction was 12%.