With the development of EFL (English as a Foreign Language) writing research, an effective writing process of EFL learners should involve functions of process writing, teacher's instruction, peers' interaction and collaboration. Process-oriented writing, focusing on the writing process, emphasizes interactivity and revision with teachers' guidance. Meanwhile, SNS (Social Networking Services) tools such as Instance Messenger (IM) and vlog have the advantage of strong interactivity and the potential of improving cooperation among learners. This study carried out an experimental research applying vlog group activities inside and outside English writing class, with the aim of investigating its effect on learners' writing performance. It integrated SNS-based multimodal composing activities into higher education, with the aim of determining its effects on learners' writing performance. Two classes in junior tertiary education (Freshmen at the American University in Cairo) were recruited, one class of 15 students as the control group without using SNS- based multimodal composing, and the other as the experimental group. While two classes'writing performance improved between pretest and posttest, the gains of the experimental group in three detailed aspects (readability, lexical complexity and syntactic complexity) were significantly larger. These findings are discussed in relation to specific characteristics of multimodal composing and SNS-based learning that enables learners to improve functional writing performance. A survey about learners' perceptions and attitudes towards vlog application in writing was also conducted among learners in vlog group. Most learners viewed vlog as an enjoyable and effective way to advance their writing performance and reduce their anxiety.