The objective of the experiment was to compare in vitro digestion techniques, i.e. 24, 48 and 72 h pepsin digestion, pepsin-small intestinal fluid (SIF) digestion and pepsin-pancreatin digestion, for the determination of in vitro digestibility of utilizable true protein (uTP) of mixed rations for sheep. Twelve typical mixed rations for sheep (CP content 7.64-13.02% DM) were formulated as feed samples. It was found that there was no significant deference in uTP digestibility of mixed rations between 24, 48 and 72 h pepsin digestion (P>0.05), whereas uTP digestibility of pepsin-SIF treatment was higher than that of pepsin treatment (P<0.05), and uTP digestibility of pepsin-pancreatin treatment was higher than that of all other treatments (P<0.05). Further research is needed to study the reasons for the difference in in vitro uTP digestibility between pepsin digestion, pepsin-SIF digestion and pepsin-pancreatin digestion, and study the relationship between in vitro and in vivo uTP digestibility before a suitable in vitro technique for determining uTP digestibility is proposed.