The previous literatures suggested that the size of the auditing firm is associated with the audit quality. And the higher agency cost of the company is the higher audit quality needed. The characteristics of the companies in Taiwan are much different from those of the companies in the United States. One of those difference characteristics is the family company. This research starts at this point and wants to find out "Does the agency cost can explain the need of audit quality in the family company environment in Taiwan." The result suggests that as the family members have more than half of the board seats, the more stocks directors holding, the higher possibility the company would engage Non-Big4. As the family members have less than half of the board seats, the more stocks directors holding, the higher possibility the company would engage Big4 in Taiwan.