Simulated diagrams of lung sections of dust-macule type pneumoconiosis were plotted with computer simulation techniques and classification criteria for dust-macule volume density were formulated with stereologic quantitative analysis to differentiate the effects of artificial factors in pathological diagnosis of pneumoconiosis, Areas of dust-macule of 100%, 75% and 50% corresponded to 41.4, 31.0 and 20.7 in dast-macule density, respectively. The pathological diagnostic criteria for pneumoconiosis were evaluated by standardized chest X-ray film with a satisfactory result. It is suggested a squared test grid with a length of 5 mm in each sides of the small checks be used in practice.