A new algorithm for designing half-band FIR (Finite Impulse Response) filters with equiripple passband amplitude is developed. This algorithm is an analytical design method with which tap-gain coefficients of FIR filters are obtained by non-iterative calculation. The minimum stopband attenuation can be reduced within the limits of appropriate quantity by permitting equi-ripples in the passband without extending the transition width of FIR filters. A method to reduce the level of equi-ripples is also mentioned.