This paper provides a description of the process in development of textbook unit on measuring length for second grade in elementary school according to action research methodology. The teaching unit development has been done based on the new national mathematics curriculum released in 2006. Mathematical communication and positive attitude toward mathematics are highly emphasized in the new curriculum. These new foci have been analysed through literature review and interviews with two incumbent teachers to be respected in the unit in an appropriate way. Three stages of development with different ways of organizing contents and different problem contexts were reported in the paper.