By using the improved strong field approximation method combined with the time window function, the effect of hydrogen atomic electron wavepacket (EWP) interference in above-threshold ionization by a strong laser field on the photoelectron energy spectra and two-dimensional (2D) momentum spectra is analyzed. It is found that the general characteristics of photoelectron energy spectra and 2D momentum spectra are formed by the interplay of inter-cycle and intra-cycle interferences. The fanlike structure in the 2D momentum spectra is caused by the long-range Coulomb potential and the intra-cycle interference. A numerical solution of the time-dependent Schr dinger equation (TDSE) is used to analyze the reason why the intra-cycle interference is suppressed in multi-cycle pulse ionization and it is found that this special fringe appears in the 2D momentum spectra only when the Keldysh parameter is close to 1. These results show that the long-range Coulomb potential has an important influence on the formation of these fringes.