Recently, the institution investors have affected greatly on the stock trading market. Besides the economic environment, the investors also use the information from the listed companies as one of the criteria for their evaluation. Thus, to conduct the investor relation (IR), the enterprises will make use of the public relations (P.R.) policy and make the company information open to the public through the mass media so that they can communicate with the institutional investors constantly as well as earn the support from them. The study is based on the collection of the secondary data analysis and the in-depth interview from the listed companies focusing on the relationship among the investors which expand the public relation policy via the message strategy, the mass media, the mutual interaction with the media and the public relation activities. Take the automotive crash parts manufacturers for example, in P.R. managing, the P.R. dep. must convince and be authorized by the managing dep. before demanding other sections of fully supporting the P.R. in setting the target, expanding the P.R. plans and evaluating its profit. In the P.R. policy and message strategy, the publicists have to control the firm information in hand, including polishing the open company info and creating more appealing topics to proceed with the mutual communication with the mass media and the institution investors. Of all the communication tools (inclusive of the current print media and electronic media), the press release, the press conferences, the investor conferences and the enterprise websites are indispensable for the mutual interaction between the listed company and the investors besides the compulsively- regulated message strategy.