This study self-builds two corpora from 55 and 50 scientific papers published on Nature. Based on developmental progression index of writing ability hypothesized by Biber et al., this study compares and analyzes noun phrases complexity in scientific papers by Chinese and American writers. Results indicate that: 1) In terms of the overall distribution of premodifiers and postmodifiers in noun phrases, Chinese writers use premodifiers more frequently than American writers; 2) Chinese writers use less complex relative clauses, nouns, prepositional phrases as modifiers than American writers because of mother tongue transfer. The findings will shed light on the writing of scientific papers for Chinese writers.