We present observations of 22 extrasolar planet host stars and derive their stellar parameters. With the high signal‐to‐noise ratio spectra, we acquire accurate metallicities and the differential abundances for 15 other elements and we discuss the relation between the abundance ratio and the metallicity. These sample stars are metal‐rich relative to the Sun, covering the range from −0.04 to 0.54 dex with the average [Fe/H] value of 0.15 ± 0.12 dex, except for HD 37124, which has [Fe/H]=−0.45. The stars with planets show a slight overabundance pattern for [C/Fe] and [Mg/Fe], but [Na/Fe], [Al/Fe], [Si/Fe], [Ti/Fe], [Cr/Fe], [Sc/Fe], [V/Fe], [Ni/Fe] and [Ba/Fe] are approximately solar in the sample stars. These stars also show slight underabundances for [O/Fe], [Ca/Fe] and [Mn/Fe]. The sulphur displays enhanced values, ranging from −0.10 to 0.40 through the sample stars. These results are used to investigate the connection between giant planets and high metallicity and to probe the influence of the process on the other elements.

With the high signal-to-noise ratio spectra, we obtained Si abundances of 22 extrasolar planet host stars, and discussed some constraints on the planet formation. Using our silicon abundance results and other authors' Si abundance studies about planets-harboring stars, we investigated the correlation between the dynamical properties and the silicon abundance. We propose a hypothesis that higher primordial metallicity in the host stars' birth cloud with higher abundance of Si will make the cloud more sticky to bypass the time scale restriction in planet formation and easier to form the planets.