Abstract: The microstrip reflectarray is composed of each unit cell, the ability of the unit cell greatly affects themicrostrip reflectarray. In this article, we firstly introduce an equivalent waveguide approach which can be used to simulate thereflection phase of the microstrip reflectarray. Then the different ratios of the patch width in different substrates, the thickness ofdielectric substrate are analyzed which affect the phase curve and the bandwidth of the reflectarray, accordingly we proposehow to obtain the maximum bandwidth in the design of microstrip reflectarray. In the end, we do some research in the differentshapes of slot structure on the ground plane which have effect on the reflection phase curve and amplitude, the results show thatappropriate slot can improve the flatness of the phase curve and the amplitude of the reflection field.