This paper presents an introduction of a 4-zone phenomenological combustion model. By using this model, mass combustion rate and NOX emission may be deduced from measured indicator diagram of D.I. diesel engines.Based on the test data of type LD1100 diesel engine, the influence of combustion system parameters and running parameters on measured results are discussed in this paper. From a measured indicator diagram, the only result of combustion rate may be deduced, but the chosen values of some parameters influence the deduced result of NOx emission.The measured combustion rates by using phenomenological model are compared with that by using thermodynamic model. In this paper, authors discuss the influence between that two combustion rates, and point out that former combustion rate more conform to the actual combustion process.