Waste vinegar residue, the by-product of vinegar processing, was used as substrate for phytase production from Aspergillus ficuum NTG-23 in solid-state fermentation to investigate the potential for the efficient re-utilization or recycling of waste vinegar residue. Statistical designs were applied in the processing of phytase production. First, a Plackett-Burman (PB) design was used to evaluate eleven parameters: glucose, starch, wheat bran, (NH(4))(2)SO(4), NH(4)NO(3), tryptone, soybean meal, MgSO(4)·7H(2)O, CaCl(2)·7H(2)O, FeSO(4)·7H(2)O, incubation time. The PB experiments showed that there were three significant factors: glucose, soybean meal and incubation time. The closest values to the optimum point were then derived by steepest ascent path. Finally, a mathematical model was created and validated to explain the behavioural process after these three significant factors were optimized using response surface methodology (RSM). The best phytase activity was attained using the following conditions: glucose (7.2%), soybean meal (5.1%), and incubation time (271 h). The phytase activity was 7.34-fold higher due to optimization by PB design, steepest ascent path design and RSM. The phytase activity was enhanced 0.26-fold in comparison with the results by the second step of steepest ascent path design. The results indicate that with waste vinegar residue as a substrate higher production of phytase from Aspergillus ficuum NTG-23 could be obtained through an optimization process and that this method might be applied to an integrated system for recycling of the waste vinegar residue.