Operation of aMOS RLC-oscillator is considered, and it is shown that it can be described by the van der Pol model. The transformation of time scale to the oscillator intrinsic time allows one to use the previously obtained results for harmonic content of the van der Pol model. One can calculate the total harmonic distortions and use it to design an oscillator with required level of them. The correction of frequency in case of strongly distorted oscillations is also given. The results are verified by design and simulation of an RLC oscillator for realization in 130 nanometer technology for communications in wireless test systems.