Based on a large diachronic corpus, the present study investigates the boundary permeability between transitive and intransitive uses of ambitransitive verbs in Present-day English. Our findings reveal that: (1)transitivity is not a fixed attribute of English verbs and the change of transitivity can be measured by boundary permeability;(2)four types of change patterns of verb ambitransitivity are identified, namely, increasing, decreasing, increasing-decreasing, and decreasing-increasing, and decreasing pattern is the dominant one;(3)the dominance of decreasing pattern reflects the conventionalization and entrenchment of verb transitivity, indicating a “Matthew Effect” in language change.