This paper proposed a generator of signals with a quadruple frequency and a triangular waveform tunable in symmetry based on the dual-parallel Mach-Zehnder modulator and balanced photodetector. In the scheme, modulation nonlinearity and multiparameter manipulation are used to generate the target signals. An approximate characterization of the photocurrent expression using the first three terms of the Fourier expansion of microwave signals following the objective function can be achieved via the adjustments of the modulation index β and time delay τ. As a result, signals with a periodic triangular waveform and a frequency four times the RF modulation frequency are obtained. In the simulation verification, 20 GHz signals with a triangular waveform are output at an RF modulation frequency of 5 GHz. Based on the fitting error, the error of the obtained time-domain waveform can be evaluated. The designed generator is capable of outputting signals with a symmetry factor between 20% and 80% while ensuring the fitting error within 8%.