Most of the existing quasi-zero-stiffness vibration isolators are of complex configuration and high cost. Aiming to these drawbacks, this work adopts a curved arch to providing quasi-linear negative stiffness and a straight beam to providing quasi-linear positive stiffness; matching and combining the curved arch and straight beam constitute a quasi-zero-stiffness vibration isolator with concise configuration and cheap cost. In theory, by the energy method we derive the analytical formulas for designing the stiffness of curved arch, straight beam and the combined system. In experiments, we obtain the force- displacement relation from static testing which verifies the efficacy of the analytical formulas, and the good isolation performance and some load adaptability from dynamic testing.