A negative tapered-double-sinusoidal grooves structure is proposed in order to form a coaxial Bragg reflector with narrow bandwidth, high quality factor Q and good selectivity. According to the coupling mode theory, on the basis of the ordinary sinusoidal groove structure, the auxiliary sinusoidal distribution with smaller etching period is superimposed, and the negative taper is added on the inner and outer walls of the conductor to form the negative tapered-double-sinusoidal grooves coaxial Bragg structure. Through FORTRAN software programming, compared with that of the ordinary sinusoidal grooves, the bandwidth of the working mode and the competing mode of the negative tapered-double-sinusoidal grooves coaxial Bragg structure gets narrower, the quality factor Q gets greater, and the residual side lobe phenomenon is suppressed. At the same time, the center resonant frequency point of the competition mode is far away from that of the working mode, the band gap overlap is further separated, and the frequency selectivity is improved. The structure design is simple and reasonable, which can better separate the working mode and the competition mode, and is favorable to construct a single high-order mode resonator with high quality factor Q and high power.