Abstract: The statistical methodology and accelerated stability tests have been employed to investigate the effects of some adjuvants and of technological process on the stability of tetracycline (TC) in aqueous suspension. A more stable new formulation for suspension B has been developed. The result of accelerated stability tests has showed that the shelf-life (t0.9) of Suspension B under room temperature (25℃) is 24.7,but that of original product A is 19 months. Both chemical kinetic theory and experiment results indicate that the solubility of TC in the liquid medium of suspension is one of the important factors which are related to the stability of TC. The degradation of TC in suspension is exhibited by pseudo-zero order reaction, while in homogeneous solution, it can be illustrated by first order reaction of which apparent active energy(Ea) is 27.73 kcal/mol.