I think i got the solution.
The folder which contains web service in web application doesn't have access permissions. so other application cannot access web service, when i added folder permissions in web.config, it is working. Also, i have added protocols in web.config as
<system.web>
<webServices>
<protocols>
<add name="HttpGet"/>
<add name="HttpPost"/>
<add name="HttpSoap"/>
</protocols>
</webServices>
</system.web>