Subcutaneous immunoglobulin (SCIG) is a new therapeutic procedure for patients with primary immunodeficiency (PI). This research is a systematic review of studies on the efficacy and safety of intravenous immunoglobulin (IVIG) and SCIG in adult patients with PI. This study includes a systematic review of cohorts and randomized clinical trials (24 articles) from 5 databases with no time limits. Random effects meta-analysis was performed for outcomes such as efficacy and safety. Standard mean difference (SMD) of serumimmunoglobulin level was equal to 0.336 (P <0.01; 0.205-0.467) and the odds ratio (OR) of side effects was 0.497 (P=0.1; 0.180-1.371). The results indicate that SCIG leads to a higher level of immunoglobulin and a reduction in side effects but shows the same infection rate as IVIG. Our analysis shows that shifting from IVIG to SCIG therapy can have clinical benefits for PI patients.