To promote cycloid application in the pump tooth profile and its performance evaluation,tooth number and contact ratio which could best reflect pump performance were taken as design parameters of cycloid tooth profile based on cycloid forming principle.The radius coefficient of moving circle was uniquely determined by the standard addendum coefficient.The neat formulas of shape coefficient of tooth profile,central angle and pressure angle of tooth tip,maximum trapped-oil flow,volume utilization coefficient,flow pulsation coefficient and displacement volume per unit were constructed in order to reflect various pump performance;finally,3D model of cycloid gear pair was designed and verified,and tooth profile parameters and performance parameters of different combinations were given.The results show that the design and construction method of cycloid tooth profile is simple and the result is accurate;the tooth number significantly affects pump performance,the more the tooth number is,the better the trapped-oil performance and pulsation performance are,but the worse the lightweight effect is;the trapped-oil performance and pulsation performance are mainly affected by contact ratio,the smaller the contact ratio is,the better the two performance are,and the influence on trapped-oil performance is greater;a little more tooth number and a little less contact ratio are the best combination to improve trapped-oil performance and pulsation performance,and is conducive to reduce the noise of gear pump.