Abstract: The biological model of monolayer anchorage-dependent cell apoptosis induced by in vitro β-ray irradiation is established to dynamically observe the cell apoptosis. The A549 cells of adenopulmonary carcinoma cultured in vitro are irradiated byβ emitting 32P-colloid and the interven-tional factors are rinsed out at regular intervals. The thickness of the absorbed dose of monolayer anchorage-dependent cells is measured and absorbed dose of the cells is calculated by the formula of internal dosimetry ofβ emitting 32P-colloid. The results suggest that the model has the characteristics of stability and repeatability. It provides an approach for observing the cell apoptosis induced by in vitro β-irradiation and calculating the absorbed dose of cells in clinical. And the mechanisms of internal irradiation therapy for solid tumors might be obtained.