This paper describes an English grammatical error correction system for CoNLL-2013 shared task. Error types covered by our system are article/determiner, preposition, and noun number agreement. This work is our first attempt on grammatical error correction research. In this work, we only focus on reimplementing the techniques presented before and optimizing the performance. As a result of the implementation, our system's final F1-score by m2 scorer is 0.1282 in our internal test set.