This research investigated the impact of processing instruction (PI) on the acquisition of the English third-person singular present tense by Chinese English-as-a-foreign-language (EFL) learners and whether this effect would extend to the acquisition of other language components. This study featured the pretest-immediate-posttest design and participants were required to participate in all tests (pretest, immediate posttest, delayed posttest). Two classes were assigned to receive PI and Traditional Instruction (TI) respectively, while another class served as the control group. A language background check was conducted 2 weeks before the main experiment. And after three consecutive class hours, there is an immediate posttest and a delayed posttest in 2 weeks. By comparing the results of the three tests, the study measured and compared the primary effects, secondary transfer-of-training (TOT) effects, and cumulative TOT effects of PI and TI. The findings showed that both PI and TI had significant effects, although they differed in the extent and duration of improvement in acquisition effectiveness. PI was found to be superior to TI, which could be reflected in primary and two TOT effects except the interpretation tasks related to passive voice. This study suggests that PI can be utilized in grammar teaching due to its efficacy in teaching specific linguistic structures and its transfer-of-training effects on other grammar rules.