A high-pressure fuel pump in a GDI (Gasoline Direct Injection) engine has been increasingly applied on passenger vehicles because of its high fuel efficiency and reduction of exhaust emissions. The design specifications of principal components of GDI high-pressure pump should be validated prior to the manufacturing. This study presents the analytical results of the specifications for the design of a GDI pump of Motonic Co. by using computational model based simulation. The results are largely divided into two parts. First, cam-follower dynamics with the proper design of cam profile, and second, the discharge flow performance of the pump in consideration of the characteristics of inlet control valve.