The purpose of this study was to investigate nondisclosure of supervisees in supervisory process.  Six counselors of master degree in practicum were supervised from four to six times. Each time when supervision ended, they were interviewed immediately, while watching the videotapes of the supervisory process.  According to the results, nondisclosure of supervisees occurred in each supervisory session.  However, the first session of the whole supervisory process had the highest frequency of nondisclosure.  With supervision proceeded, the nondisclosure has the tendency of decline.  Averagely, each supervisee had 3.96 nondisclosures in each session.  The most common nondisclosures were the information related interaction between supervisor and supervisee.  Within them, negative emotions and evaluations toward supervisor were most popular.  The effects of nondisclosures all were negative, especially centered on professional learning as a counselor.  At last, except both positive emotion and positive evaluation on supervisor did not have any negative effects, the other categories of nondisclosures all had such effects and their most significant effect was on professional learning as a counselor.  At the same time, different categories of nondisclosures had different effect patterns