The invention relates to an ultrahigh-pressure pump. In the invention, a plurality of eccentric wheel groups are arranged on a spindle, and each eccentric wheel group consists of a plurality of eccentric wheels distributed along the axial direction of the spindle; the large-diameter vertexes of all the eccentric wheels are sequentially and uniformly distributed along the circumference with the spindle as a circle center; the parts on the circumference corresponding to each eccentric wheel is provided with at least one pair of radially opposite plunger pumps, and the cylinder body of each plunger pump is arranged on a base; the outer end of a push rod plunger of each plunger pump is provided with a roller through a guide sleeve, and the outer circumferential surface of the roller is butted against the outer circumferential surface of a corresponding eccentric wheel; each plunger pump is provided with a water feed pipeline port and a water drainage pipeline port; and the spindle is connected with a power device through a transmission shifting mechanism. The pump has the advantages of being used for borehole and well cementation fracturing construction of oil drilling and developing engineering, being capable of greatly improving the mechanical drilling speed, shortening the drilling period and reducing the cost and having high, uniform and stable pump pressure, smoothness of repairing and replacing without stopping the pump and long service life.