This paper focuses on unit maintenance market design in the transition period of power market. The maintenance market design scheme is easy to transit from the unit maintenance approval mechanism by planning mode into market mechanism. Every unit owns maintenance right and the first step of maintenance market mechanism is to transform the maintenance right for unit into fictitious money. Then the maintenance right market is established in some special period for a year. Generators bid in the right market with the fictitious money allocated. The bidding result decides the maintenance plan in a year for every unit. This paper also proposes a monthly adjustment mechanism for maintenance plan decided by market

and suggests a premium and punishment scheme for maintenance behavior of unit in the end of year. Finally

a simple example is given to demonstrate the introduced maintenance market mechanism.