This article presents a hybrid de-embedding method by combining the unitary condition of lossless networks and the impulse response curve truncation. A magnitude-symmetry formula is derived for reciprocal and low loss printed circuit board (PCB) fixtures. It gives the analytical relationship between $S_{11}$ and $S_{22}$ for asymmetric PCB fixtures. At the same time, the impulse response curve truncation is used to solve $S_{11}$ . Based on above two methods, the number of fixture’s unknown $S$ -parameters is reduced. The reasonableness of the magnitude-symmetry formula is verified by simulated fixtures, which are commonly used in radio frequency and microwave engineering measurements. The accuracy and feasibility of the proposed hybrid de-embedding method are also numerically and experimentally verified. Good $S$ -parameters correlations of fixtures and devices under test (DUT) can be observed in all examples.