Abstract: This paper is one of a series of reports on speech development of preschool child-ren. This paper analyses the structure types and the developmental trend of the mostfundamental sentences-simple, affirmative, active and declarative. The Ss were seventy preschool children (2 to 6 years of age, 33 male and 37female) randomly drawn from two kindergartens and two nurseries and divided intoseven age groups (2, 2(1/2), 3, 3(1/2), 4, 5, and 6 years) with 10 Ss each. The subjects'spontaneous speech was recorded with a tape recorder. Each subject was recordedtwice within two weeks, each recording lasted for half an hour. A total of 3459 simple declarative sentences were recorded and nine structure typesranging from simple to complex were discovered. According to the distribution of thesetypes in each age group, the developmental trend of the structure of preschool child-ren's fundamental sentences was as follows: 1. from chaos to gradually differentiating; 2. from looseness to gradually well-knitting; 3. from contraction and stereotype to gradually expanding and being flexible.

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