A finite volume time domain method is developed for in-plane vibration based on mixed triangular and quadrilateral elements. Here the linear quadrilateral element shape function is introduced instead of the constant one to improve the accuracy of the present method. The improvement is validated to be vital to avoid violent numerical oscillation of displacement fields when applying to the point–source problem. The present method is proposed to analyze the transient responses and the natural characteristics of several in-plane problems. The results show good agreement with the commercial code solutions and the analytical solutions. In order to demonstrate the capability of the present method for multiexcitation problems, an example with sources containing different frequencies and phase angles, concentrated and uniform distributions, and impulse and continuous forms is analyzed.