The plasma sensitivities of different kinds of primary explosives were studied. The voltage-time curves,current-time curves and light-time curves were obtained. The data were analyzed by using D-optimization method. Results show that lead styphnate (LTNR)，nickel hydrazine azide （NHA） and B/Pb3O4 are ignited by the SCB heat; lead picrate,lead azide,nickel hydrazine nitrate(NHN) and barium styphnate are ignited by the SCB plasma. The order of plasma sensitivity is: lead picrate>lead azide>barium styphnate>nickel hydrazine nitrate.