Introduction: this study is conducted to investigating The effectiveness of anxiety-regulation short-term dynamic psychotherapy(STDP) on defense styles and emotional expressiveness in social phobia patients. Method: This project is a kind of multiple – baseline experimental single case study (Kazdin, 1992). Sample includes six cases and they are selected based on purposeful sampling. This intervention is conducted based on McCullough's manual for short term dynamic psychotherapy. McCullough's short term dynamic psychotherapy was prepared for restructuring defences, affects and attachments (McCullough. 1997). In general, this study have three phases. The first phase is baseline evaluation, the second phase is intervention and the third phase is three months of follow up. Intervention includes 20 weekly therapeutic sessions (each session 45 minutes) based on the manual. Instruments in this research are Defense Style Questionnaire(DSQ),Emotional Expressiveness ##Questionnaire (EEQ),social phobia inventory(SPIN), Global Assessment Function(GAF) of DSM-IV. Two methods, clinical significance and recovery percent formula are used for data analysis. When individual's scores in target problems decreased to the normal level, it concluded that results clinically are significant. In other words, individual's scores in inventories must decrease below the cut-off point to be consider clinically significant. Recovery percent formula is one of the methods to assess client's progress in decreasing target problems. More than 50% recovery in results is considered clinically significant (kazdin, 1992). Key words: social phobia syndrome,defense styles, emotional expressiveness, short term dynamic psychotherapy.