Language is an important ability and tool in human societies, however, there is no single way in which learn to communicate. Although each child follows an individual developmental pattern, language development requires basic vocabulary ability. Vocabulary ability related with amount and quality on vocabulary is a core in language development. The purpose of this study was to investigate children's difficult degree on basic vocabulary ability to teach vocabulary for children with disabilities. The vocabulary was selected mixed method which is combined with subjective and objective method in vocabulary selection methods. One hundred vocabulary items which include five vocabulary on one plate. Therefore five hundred vocabularies were selected. The subjects were 939 kindergarten and elementary children. After test the difficult degrees in each items were manipulate to keep validity to use regardless specific items which means the items have high validity as .90. Also, score table based on mean and standard deviation were analyzed. This research suggested that (a) this study in limited on comprehensive ability on vocabulary, therefore productive ability on vocabulary needs for following study; and (b) written language ability based on basic vocabulary is needed for next study.