Abstract
The purpose of this paper is to improve the English teaching levels of colleges and universities. First, the primary attributes of dynamic nonlinear system theory in second language acquisition are analyzed. Second, the influencing factors of English grammar application ability in theoretical dimension and measurement methods are proposed. Six first-year students majoring in English in a university were randomly selected as research objects, who were followed up for a semester, during which three identical oral English tasks were finished (in September, October, and November of 2020). The fluency, accuracy, and complexity of students' utterances are statistically analyzed using SPSS 26.0. Results demonstrate that the fluency of students' utterances has increased from 110 syllables per minute on average in September to 129 syllables per minute on average in November. The proportion of error-free clauses has increased from 0.5 to 0.55, and the number of clauses in the T unit has increased from 1.42 to 1.51. Students P-1, P-2, P-3, P-5, and P-6 have a gradually increasing accuracy of utterance, while student P-4 shows a gradually decreasing utterance accuracy. Students P-1 and P-5 have a decreasing utterance accuracy, while students P-2 and P-6 present an increasing utterance accuracy. Besides, the utterance accuracy of students P-3 and P-4 first decreases and then increases. The performances in utterance complexity of students P-2, P-3, P-4, P-5, and P-6 have been increasing gradually, while the performance of student P-1 has been decreasing gradually. The normal distribution of each student's test scores is different, as well. Hence, any minor changes will affect the overall oral English levels of students.