Abstract: In order to investigate the effect of uncertain design parameters on the performance of cluster plug nozzles in design method,two types of 8-module and one type of 16-module clustered plug nozzles were designed with the same total area ratio and shape size.Their thrust efficiencies were calculated numerically,and also compared respectively under the condition of same module gap and diameter ratio,module number and module area ratio.The 8-touched-module clustered plug nozzle with module area ratio of 30.2 had the highest efficiency in high attitude and the 8-separated-module clustered plug nozzle with module area ratio of 20.7 had the highest efficiency in low attitude.In the design procedure,a bigger module area ratio can be selected to enhance its performance when the clustered nozzle works in medium and low attitude,otherwise a smaller one can be selected.