Changes of protease,amylase,algalase and cellulase activities in alimentary canal were analyzed in sea cucumber (Apostichopus japonicus) weighing 165.3 ± 3.1 g collected monthly along Dalian coast from November 2004 to October 2005.The results showed that the ratio of digestive tract length to body length (RDTLTBL) was 4.6-5.9 from January to May,with the peak in February in the sea cucumbers.Meanwhile,the activities of protease,amylase,and algalase increased with water temperature rising,the maximum value in April and May.Afterwards,there was decrease in the (RDTLTBL) as water temperature rose,0.8-1.1 from August to early October.In the same period,the activities of protease,amylase,and algalase decreased gradually.While the water temperature decreased in middle and later October,the (RDTLTBL) and the activities of protease,amylase,and algalase increased rapidly.There was low and constant cellulase activity all of the year.