Abstract: New formulations were developed to increase the relative bioavailability of ibuprofen tablets produced by Shan Dong Xin Hua Pharmaceutical Factory in China. The dissolution rates of the tablets available in the Chinese market(A), the tablets of the new formulations (B and C) and the reference tablets made by British Boots Company (D) were determined. Human bioavailability studies were conducted to assess the in vivo performances of A, B and C relative to D by GC. The particle sizes of ibuprofen raw materials (A′, B′, D′) used for producing tablets (A, B and C, D) were ascertained and the differences of crystal forms between A′ and D′ were compared.The crystal forms of A′ and D′ were found to be the same, with no phenomena of polymorphism occurring, The mean surface area diameters of A′, B′ and D′ were 130.0, 36.6 and 56.6 μm respectively. Mean dissolution time (MDT) in vitro for A, B, C and D was 21.95, 5,322, 12.41 and 12.37 min respectively, In vivo, formulation A was bioinequivalent to D. The new formulation B was bioequivalent to D from the extent of absorption, while B was superior to D in the rate of absorption. The new formulation C exhibited an absorption effectiveness higher than D. Moreover, the percent of ibuprofen absorbed at time t after drug administration was correlated with the dose dissolved in in vitro test at time t/5 (p<0.01). The higher relative bioavailability of B and C over A was related to particle size of ibuprofen material, formulation and technological process.