Optical microsphere (OM) cavities supporting Whispering Gallery Modes (WGMs) have received much attention because of their high quality factor (Q). The study analyzes the Fabry-Perot (FP) cavity and OM cavity theories. An OM cavity with diameter of 1.2 mm was produced by melting a silica optical fiber using a CO2 laser, and the coupling structure for OM cavity and tapered fiber was tested. We designed an OM cavity frequency stabilization system based on basic PDH frequency stabilization system. Absorption and dispersion characteristics of error signal curves used to be frequency discrimination curves were analyzed. We compared the relationships between error signal slopes and different modulation frequency, OM cavity′s diameter, coupling loss, transmission loss. The results show that the maximum Q factor of OM cavity coupled by the tapered fiber is 1.1×108. Transverse electric (TE) mode and transverse magnetic (TM) mode can be transformed to optimize coupling efficiency. The transmission spectrum of the second radial mode was obtained by matching dimensions between OM cavity and tapered fiber. The slope of the error signal is 15.4 A mW/MHz. Our work shows its potential to improve the sensitivity of the PDH technique.