A non-equilibrium plasma can be generated by applying microwave power to an La0.8Sr0.2CoO3 sample under an argon gas flow. However, since the plasma generation mechanism has not yet been fully understood, we investigated the effect of La1-xSrxCoO3 on plasma generation by varying x in La1-xSrxCoO3 from 0.0 to 1.0. As a result, we found out that the plasma could be generated by using samples whose x in La1-xSrxCoO3 was between 0.0 and 0.6. The temperature rise of these samples (0.0 less than or equal to x less than or equal to 0.6) during microwave irradiation was much higher than that of other samples (0.8 less than or equal to x less than or equal to 1.0) which had no ability to produce a plasma. The low work function of the sample also affected the ability to produce a plasma. In conclusion, we considered that the prime requirement for the ability to produce a plasma would be a large increase in temperature of the sample during microwave irradiation, and that the sample would play roles of both triggering and maintaining the plasma.