Phases of Bessel beam and self-imaged bottle beam along propagation axis are analyzed. Phases of ideal Bessel beam and Bessel beam generated by axicon along propagation axis are periodic saw-toothed distribution after analysis with diffraction theory. And phase of self-imaged bottle beam generated by interference of two Bessel beams is also saw-toothed distribution, while phase singularity is found at the zero intensity position. In simulation experiment, the minimum intensity of self-imaged bottle beam on axis is not zero, therefore there is not phase singularity on axis. The result of research is valuable in generating self-imaged bottle beam by phase modulation, whose dark field is zero.