The invention provides a wideband and low-phase noise local frequency synthesizing circuit. The wideband and low-phase noise local frequency synthesizing circuit includes a direct digital frequency synthesizer, frequency multipliers, low-pass filters, high-pass filters, a band-pass filter, a quadrature mixer, a mixer, amplifiers, an integer frequency divider, a phase discriminator, a loop filter, a voltage-controlled oscillator and a coupler. According to the wideband and low-phase noise local frequency synthesizing circuit of the invention, high phase discrimination frequency is adopted perform phase discrimination, and therefore, phase noise deterioration of a loop can be decreased; the loop adopts the integer frequency divider, and therefore, the effects of the mantissa of fractional frequency division on phase noises can be eliminated; baseband signals generated by the direct digital frequency synthesizer are subjected to quadrature up-conversion, so that high-resolution, low-phase noise and high-frequency signals can be generated, and the high-frequency signals and the output of the voltage-controlled oscillator are subjected to mixing down-conversion, and signals obtained after the down-conversion can become signals with large step. Since the output of the voltage-controlled oscillator and the high-resolution and low-phase noise signals are subjected to the down-conversion, the input frequency of the integer frequency divider can be reduced, and the frequency division ratio of integer frequency division can be decreased.