The poem Lines Sent to the North Written during Night Rains is one of the most famous poems of the late Tang poet Li Shangyin. It is widely favored by translators and has many English versions. Through the literature research, it is found that there are few studies of its English versions combined with the linguistic tool of transitivity. This paper aims to study the poem Lines Sent to the North Written during Night Rains and its three English versions from the perspective of system-functional linguistics, taking the concept of transitivity as a theoretical tool, supplemented by the theory of functional equivalence to evaluate the three English versions. According to the results of transitivity characteristic analysis and functional equivalence evaluation, it is found that keeping the transitivity characteristics of the original and the translation consistent is actually a kind of application and embodiment of the principle of functional equivalence, and the change of transitivity characteristics does not necessarily violate the principle of functional equivalence, because in specific circumstances, the transformation of process types can also help to achieve the effect of meaning equivalence, reproduce the artistic conception, and finally realize the goal of functional equivalence.