This study investigated the factors affecting null subject acquisition of Korean learners by looking at their pattern of null subject usage in the spoken data. The participants were first divided into three groups(sentence-oriented group, discourse-oriented group and control group) and then went through a data analysis on their patterns of null subject usage. Then, two experiment groups were divided into 2 groups again according to their residence period in Korea for further analysis. The results of this study are as follow: (1) The rate of null subject usage by native Korean speakers was found to be an average value of 71.7%, sentence-oriented group learners 79.3%, discourse-oriented group learners 54.1%. (2) There were no significant differences in null subjects usage for both sentence-oriented control group and discourse-oriented control group. (3) Participants with Korean residence period of 9 months or more showed similar patterns with native Korean speakers on null subject usage regardless of their first language. Overall, the results of this study supported full access hypothesis.