Bilingual lexical acquisition, representation and processing are closely related issues in the study of mental lexicon. Empirical investigation of the processing mechanism can reflect the mental representation, the progress of which in turn pilots pedagogical theories in practice. The present study explores the role of word fossil status in bilingual lexical representation and processing through a rating task, backward and forward word-translation tasks and a word-recognition task implemented by 40 proficient Chinese-English bilinguals. Response times, error rates and omission scores indicate that there is a significant difference between pre- and post-fossil words in terms of their processing. Word frequency effects are found on words of the two fossil statuses. However, the effects are reversed: high-frequency words are responded to faster than low-frequency words when both are pre-fossil words; in contrast, as for post-fossil words, response times rise with the increase of frequencies. The findings show that word fossil status is a determinant in bilingual lexical representation and processing. The present study slightly revises the current bilingual lexical representation and processing models and enriches L2 vocabulary teaching and learning. Empirical research on the issue also tentatively tests the L2 lexical developmental theory for the first time.