The patient's expectations (placebo effects) refer to the anticipation or the belief about what is to be encountered in a consultation in the healthcare system. Currently, it is a hot-spot for researching its influence on clinical outcomes of acupuncture and moxibustion interventions. How to evaluate the magnitude of patients'expectations is a problem needing to be solved urgently at the moment. The authors of the present paper make a summary about researches on the mechanism of expectations. For example, placebo analgesia was related to decreased brain activity in pain-sensitive brain regions (thalamus, insula, and anterior cingulate cortex), and to the increased activity of the prefrontal cortex showed by fMRI, and to the release of endogenous opioids. In addition, the authors also introduce some methods (psychological scales) for assessing expectations and related influencing factors (physicians or acupuncturists, and medical environment) for future research in this area. In the coming clinical trials on acupuncture or moxibustion treatment of clinical disorders, we should further better our experimental design, and try our best to exclude placebo effect-associated or expectation-induced bias of clinical outcomes for confirming the therapeutic effects in the treatment of different clinical problems.