Abstract: The purpose of this paper is to discuss the quality of seismological recording instruments, especially to examine some instrumental components and their parameters that may influence the character of the first motion. We suggest to use the rise time ts as a parameter to characterize the recording quality of the first motion. A relation between the rise time and the frequency baud of the instrument has been obtained. The rise times of a number of seismographs installed at our seismographical stations in China are compared.