Abstract: An algorithm of extracting key actions in sign language was brought out in this paper.In the continuous and complex sign language,the number of key actions is small and the state is relatively stable.Thus using the key actions to construct the data model of the sign language will reduce the unstable factors and improve the accuracy.In this paper,an adaptive classification algorithm was proposed,which extracts the key actions step by step according to the time order and the irrelevance among the key actions.Experiments show that the algorithm can be used for the non-specific population.Moreover,the algorithm can extract all the key actions from both the single vocabulary and the continuous sentence.Key actions can be regarded as primitives of sign language,and thus sign language can be looked upon as different combinations of those primitives as well.Therefore,as for the continuous and complex sign language,the extraction of key actions has important significance not only for the data model construction,but also for its recognition.

Key words: Motion-control device, Continuous and complex sign language, Key actions, Sign language recognition