OBJECTIVE： To study the method of measuring the in vitro dissolubility of lansoprazole enteric－ coated tablets and to find out the difference between the dissolubility of lansoprazole enteric－ coated tablets and that of lansoprazole enteric－ coated capsules.METHODS： To establish a measuring method of the dissolubility of lansoprazole enteric－ coated tablets and compare the dissolubility of lansoprazole enteric－ coated tablets with that of lansoprazole enteric－ coated capsules and to acquire the dissolving parameters for variance analysis.RESULTS： (1)The accumulative dissolving quantity of the both preparations exceeded 80％ in 30 minutes.(2)The comparison of Weibull parameters,T50,Td and m,between each other in group A showed no significant differences(P>0.05).It was the same for those of group B.(3)The parameters,T50 and Td,of group A,in comparison with those of group B,showed significant differences(P<0.001).The times needed for dissoiving 50％ and 63.2％ of quantity in group B were both shorter than those in group A.The m parameters in different groups had no significant differences(P>0.05).There was no significant difference in slope of equation between two groups.CONCLUSION： This measuring method of the in vitro dissolubility of lansoprazole enteric－ coated tablets is simple,convenient,accurate,stable,feasible and good in repetition.It is concluded that there is significant difference between the dissolubility of the two dosage forms of enteric－ coated preparation of lansoprazole.