The invention relates to a mask plate, a lens array, a preparation method of the lens array and a display panel. The mask plate comprises at least one pattern unit, wherein each pattern unit comprises a transparent substrate and a semi-transparent film arranged on the transparent substrate, and the transmissivity of the semi-transparent film is gradually changed at least along a first direction vertical to the thickness direction of the semi-transparent film in the pattern unit. The lens array comprises at least one lens unit. The preparation method of the lens array comprises the step of forming the lens array by virtue of the mask plate through a photoetching process, wherein the pattern units of the mask plate correspond to the lens units one by one. According to the preparation method, the process is simple and the cost is low. The display panel comprises the lens array. By virtue of the reflection of light through the lens array, the technical effect that the view angle of the display panel is adjusted is achieved.