In this study, Semi-Quantitative FMECA for reliability analysis of solid propulsion system is performed. The FMECA is composed of two separate analyses, the Failure Mode and Effects Analysis (FMEA) and Criticality Analysis (CA). In order to carry out FMECA, the structure of the solid propulsion system is divided into 43 parts down to the component level and FMEA is carried out at the design stage considering 137 potential failure modes. Then the criticality analysis is followed for each failure mode, in which the criticality number is estimated using the failure rate databases. As a result, the relationship between potential failure modes, causes and effects, and their risk priorities are evaluated qualitatively. Also, 18 failure modes are chosen as those with the higher criticality and severity that should be improved with priority and a series of design or material changes are made for the improvement of reliability.