Abstract: By means of interventional paradigm and method of medium stimulation, 112 seventh grade students were randomly selected as participants, a series of self-constructed materials and instruments were employed to investigate three conditions for key-letters method effect in memorizing English vocabulary:recognizing key-letters, retrieving isomer word for key-letters, and retrieving definition of isomer word.The results were as follows:(1)when requested to give exact recalls, for both short-term and long-term memory, recognizing key-letters and retrieving isomer word for it were necessary conditions for key-letters method effect, and retrieving definition of isomer word was a sufficient condition for the effect;(2)when requested to give rough recalls, for long-term memory, recognizing key-letters was a necessary condition for the effect;retrieving isomer word for it was a potentially sufficient condition for the effect, and retrieving definition of isomer word sufficient condition for the effect.

Key words: keyword method, key-letters method, method of medium stimulation, higher memory, junior school student