A new scheme to trap cold atoms (or cold molecules) by an improved blue-detuned hollow optical trap is proposed,which is formed by an optical system composed of a binary phase plate and a circular aperture illuminated by a plane light wave. The dependence of the relative intensity of the optical trap and its well depth on the phase φ of the binary phase plate is studied,and some analytical relations between the geometric parameters of the optical trap and the parameters of the optical system are derived. It is found that the binary phase plate can be used to improve the intensity profile and produce a hollow optical trap with higher effective intensity and larger trapping volume. In particular,when a 100 W frequency-doubled Ytterbium fiber laser with a wavelength of 540 nm is used to illuminate the optical system composed of the π phase plate and the circular aperture,the optical trapping potential for 87Rb is about 80.2 μK. So this scheme is not only simple and convenient in the manipulation and control of cold atoms (or cold molecules) but also has wide potential applications in the fields of cold atomic and molecular physics,atom and molecule trap,life science,and so on.