The transparency of the semi-permeable membrane coating on the push-pull osmotic pump tablets is very important for the identification of the drug layer and the push layer in laser drilling machine.In the process of semi-permeable film coating,the phenomenon of whitening of semi-permeable membrane occurs from time to time.In this paper,the push-pull osmotic pump tablets coated with cellulose acetate as semi-permeable membrane with the brownish red tablet cores were prepared,and color difference anal. was adopted to evaluate the transparency of the semi-permeable membrane with delta E(DE) value as a quant. indicator.The JMP 10.0 statistic software was used to carry out the random customized exptl. design for 12 experiments,including one central point.The influences of the selected coating process parameters including inlet airflow volume,inlet temperature,liquid spraying rate,coating weight gain and relative humidity of actual environment on transparency of the semi-permeable membrane were investigated.The results showed that the influences of liquid spraying rate,inlet temperature and their interaction significantly influenced transparency of the semi-permeable membrane,and bed temperature and its interaction with relative humidity of actual environment were also significant factors leading to film opacity.