The aviation process of multiplane combat with data link system is studied in this paper. Based on the logarithmic method, a calculation method of air combat effectiveness assessment supported by data link is given and is converted to the average battle effectiveness level which is verified to be equivalent to and consistent with the air combat effectiveness assessment by mathematic theory. Based upon the improved Lanchester equation air combat model which reflects the data link function, a Lanchester air combat model under multiplaneconflict condition is set up. Based upon the four preset air combat processes and two multiplanecombat scenarios and with the examples of doubleplane confrontation, the air combat process under four different circumstances are simulated and analyzed. Further analysis is made on the influence data link on multiplane air combat, which provides the simulation data and the exhaustion chart. The result shows that under the data link can improve combat effectiveness and reverse the combat result. Moreover, the doubleplaneaircombat effectiveness is raised by about thirtyfive percent.