Abstract: To discuss the performance effects of plug truncation ratios, cold-flow tests were performed for 80%, 40%, 30% and 20% truncated aerospike nozzles by employing cold air as propellant. The test system apparatus and thrust measurement were introduced. The experimental altitude characteristics curves of the thrust coefficient efficiency were obtained. The results show that the efficiency of aerospike nozzles with bigger truncation ratios is higher than with smaller ratios, and the distinction of different truncations was minished with the pressure ratio increasing. The influence degree of the truncation on the thrust coefficient efficiency falls down by increasing the ratio. The performance loss is more due to selecting too small value of the truncation ratio. With too big ratio value the length of plug is much long, and the weight of plug increases much, but the nozzle performance elevates a little. Generally the truncation ratios can be chosen from 30% to 40%.