Chiromantes dehaani, as one of the dominant species in intertidal regions of the Yangtze estuary, plays an important role in the ecosystem. To study allometry and maturity in different phases, morphological data had been collected from October in 2009 to September in 2010. Morphologic data such as carapace, cheliped and abdomen were processed by cluster and piecewise linear regression analyses. Discriminat function and logistic curves were built to determine different phases and sizes at 50% maturity, respectively. The results showed that the cheliped width in males and abdomen width in females both presented obvious allometry. The sizes of 50% morphometric maturity occurred at 16.36 mm and 18.22 mm carapace width in males and females, respectively. The life history of males could be divided into three phases while that of females only had two phases according to different growth rates. A significant change in allometry of juvenile males with a break point was detected at 11.78 mm carapace width; carapace width of juvenile and adult females overlapped in a range of 13.04 - 18.64 mm. The crabs attained 50% physiological maturity at the size of 17.50 mm and 17.20 mm for females and males, respectively. For male, the size of morphological maturity was larger than that of physiological maturity, which was opposite to that of female.
