The marketing field is changing simultaneously with the digital world and social media influencer marketing would be a good alternative to other old types of marketing. The authors sketched the literature of social media Influencer marketing and conducted a survey in Ho Chi Minh City. The authors find that consumers tend to trust in influencers strongly and the consumer’s purchasing intention is significantly impacted by four factors including the trust of influencer, the quality of content, the relevance between influencer and product, the involvement of consumer. The result shows that the trust of influencer is a key component of influencer marketing.