Very young foreign language learners are increasing significantly in number worldwide, however, studies on this population are few. The current thesis take Chinese preschooler’s English learning in China as focus, exploring their learning behavioural development in class (based on two case studies) and the significant predictors on their English outcomes (based on two group studies). Cutting edge statistical approaches, such as recurrence analysis and Baye’s factor analysis, haven been used in the four studies. The case studies demonstrate the rich variations in terms of early English learning behaviour in class at interpersonal and intrapersonal levels. Children are varied in the timing and amount of using verbal and nonverbal behaviours in English class and such huge variation is probably related to their temperament. These findings contradict the widespread misconception in the ELL field that young children are alike and there is no need to investigate their differences. The two group studies show that both internal factors (e.g., phonological short-term memory) and external factors (e.g., home English literacy environment) play a role in early English acquisition. Compared with internal factors, external factors (or environmental factors) are more crucial in early EFL development. English input and usage should be ample; otherwise, the benefits of early FL programs might be limited. This is in line with the argument of Usage-based Theory that language is constructed during usage events.