In this paper, we designed and implemented a computer assisted writing system and the application domain is love letter. The system includes text generation module, synonym substitution module and simile expression module. A text generation model is proposed based on keyword generation model and sentence generation model. The keyword generation model extracts important keywords from the corpus and they will become the backbone of the template. Meanwhile, the sentences between keywords will construct the content of the template and candidate sentences are retrieved from the corpus based on statistical analysis. Synonym substitution and simile expression are two modules that could enrich the content of the text. Synonym terms are retrieved from the Internet and a simile expressions discovery mechanism is proposed to collect related simile expressions. The prototype system has shown that it could work well on love letter application domain and the concept of this research could be extended to another domain with minor modification.