English Present Perfect is notoriously difficult in L2 tense and aspect acquisition. Having tracked 103 Chinese EFL learners for 76 weeks during which their English compositions are collected at termly intervals, the present study investigates the synchronic and diachronic features of the English present perfect used in the compositions. Data analysis shows that during 76 weeks, frequencies of the present perfect in the compositions exhibit a “fall-rise-fall” trend, and frequencies of 3 types of errors fluctuate and end in significant decline or even disappear. The findings conform with the “Saliency Hypothesis” but disagree with the “Form-Before-Meaning Hypothesis”. The study suggests that L2 tense and aspect acquisition is a complex dynamic system; due to the influences of multiple factors, the form and meaning of L2 tense-aspect are unlikely to be acquired in a fixed order; the proficiency development of L2 tense-aspect exhibits complexity and dynamicality rather than linearity.