The comprehensive textural coefficient of arenaceous rocks can be used for analysis of sedimentary environments. A formula for defining the textural maturity of arenaceous rocks is put forward based on microscopic grain-size analysis in thin sections. The aim that we proposed this iormnla is to establish a numerical relationship between sorting and roundness of gains as well as matrix content and maturity of rocks. "hhe comprehensiva textural coefficient can be obtained according to the following formula: T=(SoΦPo)/(PΦC) Since the roundness of a grain is determined under a petrographic micro- scone, it is always smaller in thin section. The projecting of a grain often reflects its angular Goners and grain roundness is corrected by (Po2+(R-A)2)0.5 The developed comprehensive textural coefficient Td is thus Td=SoΦ[P02 (R-A)2]0.5/(PΦC) In most cases Td is similar to T. When grains are very well rounded, Td is more useful for checking the superm ature sandstone. Four maturity stages are divided, i. e. immature(T<10)，submature (T= 10-40)，mature (T=40-100)，and supermature (T or Td>100). The usage of the comprehensive textural coefficient is illustrated by some examples in this paper.