Abstract: ECSL is an equation-oriented continuous system simulation language which can be used to simulate the linear and nonlinear systems of the order of 200.Using this language,the source program Written in the state equations of the system is explicit and comprehensible.ECSL is compatible with FORTRAN and even more powerful with the system program coded in ANSI FORTRAN,this language is essentially machine-independent.This paper gives a briefing on the features and rules of ECSL as well as the basic construction of its system program.