OBJECTIVE To establish a criterion for dissolution by variables. METHODS To derive the criterion formula A=|M-D|+α/(e|M-D|×b+1)+kS by using probability theory and Statistics，and to compare between criteria by variables and by attributes. RESULTS The criterion by variables was the strictest one. The second was the criterion of Ch.P(2005). The third was the criterion of USP32. The repeat test rates from low to high were Ch.P(2005)，Criterion by variables and USP32 respectively. The sample contents were 6.43，7.82-7.98，11.60 for Ch.P(2005)，Criterion by variables and USP32. CONCLUSION The criterion by variables could control the uniformity of dissolution，and was stricter than criteria by attributes.