Which is the most early type star with a planet discovered by radial velocity method?

The answer to this, and other questions of its kind about exoplanets, can easily be found at the website http://exoplanets.org/ This site contains a very authoritative catalogue of exoplanet discoveries and has tools to enable tables and plots of many variables to be constructed.

For example, to handle your question, I produced the following plot for exoplanets discovered using the doppler radial velocity technique. This shows effective temperature of the parent star on the x-axis, versus projected exoplanet mass $Msin i$. The the hottest star with an RV-identified exoplanet (on the website, you can click on the points) is HD113337, an F6V-type star discovered by Borginiet et al. (2013). The next hottest is HD103774, which is given a slightly earlier spectral type of F5V. These two are joint hottest within their uncertainties. Just a touch cooler is Tau Boo.

It is difficult to find exoplanets around high-mass main sequence stars using the doppler method because of the paucity of strong, narrow spectral lines. Most of what we know is from observations of subgiant stars - i.e. stars that would have been early-type stars on the main sequence, but which have cooler photospheres after they have left the main sequence. HD102956, mentioned in another answer, is an example if this - i.e. it was an early-type A star on the main sequence.