In order to solve the problems of present quartz crystal microbalance ( QCM ) measuring instruments, such as high demand for crystal cutting technology and uncomprehensive measurements for crystal parameters, a modified quadrature demodulation-based method was proposed with broadband adaptive response capacity and high frequency resolution. Moreover, it is also capable of measuring both resonant frequencies and dissipation factor D synchronously and continuously. Experimental results at room temperature indicated that the adaptive frequency range was 1-9 MHz while the frequency resolution was less than 1 Hz, measured resonance frequency shifts of crystals in the range scale linearly with the equal thickness increments of poly acrylic acid ( PAA) membrane on the working electrode, and with the volatilization of different solvent factor D is measured continuously and effectively along the time axis. To sum up, compared with traditional ones, this new method has lower material cost and more obtained parameters.