I found solution. You can use argLine to fix it:
<plugin>
<groupId>org.scalatest</groupId>
<artifactId>scalatest-maven-plugin</artifactId>
<version>1.0-RC2</version>
<configuration>
<reportsDirectory>${project.build.directory}/scalatest-reports</reportsDirectory>
<junitxml>.</junitxml>
<stdout>W</stdout>
<htmlreporters>./html</htmlreporters>
<filereports>WDF TestSuite.txt</filereports>
<suites>test.common.Login,test.common.Logout</suites>
<argLine>-Dfile.encoding=UTF-8</argLine> <!-- add this line-->
</configuration>
</plugin>