Tensile mechanical properties of HMX based brittle explosives were investigated by Brazilian test with arc compress head and LVDT, and the difference between the results of the Brazilian test and single-axis tensile test was also analyzed by the t check method. For the brittle PBX-HMX, results show that PBX-HMX′s break strength and break strain tested by arc compress head Brazilian test are very close to that of the single-axis tensile method when the radius ratio of sample to the arc compress head is 1:1.35. Then, mechanical properties of three kinds of casting explosive were obtained at ratio of 1:1.35 by arc compress head Brazilian. The mechanical properties of casting explosive tested by two methods show the same trend and are very close too. So the arc compress head Brazilian test can be used to determinate the tensile mechanical properties of PBX. Howere, the t check analysis shows that there are still some differences between the two methods, the arc compress head Brazilian test can not replace tensile method completely.