Abstract: Based on the resource-based and institutional perspectives, this paper aims at investigating how standard-setting alliance portfolio size and diversity influence firm technology standardization capability. Based on the panel data of Chinese vehicle manufacturers from 1999 to 2013, the empirical analysis results show that standard-setting alliance portfolio size and diversity are positively and significantly related to the firms’ technology standardization capability, and the effect of alliance portfolio size is stronger than that of alliance portfolio diversity. However, alliance portfolio size and diversity jointly and negatively influence firms’ technology standardization capability. Further, the relationship between government and market weakens the effect of alliance portfolio diversity on firms’ technology standardization capability. Network density strengthens the effect of alliance portfolio size while it weakens the effect of alliance portfolio diversity on firms’ technology standardization capability.