Add a link to the Module list page In a Module list page (admin/modules) , We could see help, permission or configure links in Operations column. and also Module Filter customize it as a dropdown for each module listed. 

Now I need to create a new link in that operations for every module installed. How should I do it?

I think I should go with hook_page_alter() but don't know how to start with since the $page array of admin/modules page is too long.
The system_modules() form is the one that provides that module list.

You can form alter that in a custom module like so:

/**
 * Implements hook_form_FORM_ID_alter().
 */
function MODULE_NAME_form_system_modules_alter(&amp;$form, &amp;$form_state, $form_id) {
  // Loop through the array of module packages.
  foreach (element_children($form['modules']) as $package) {
    // Loop through the array of module rows for each package.
    foreach (element_children($form['modules'][$package]) as $module_filename) {
      // Add an extra operation link for each module row.
      $form['modules'][$package][$module_filename]['links']['new_operation_link'] = array(
        '#type' =&gt; 'link',
        '#title' =&gt; t('Link text'),
        '#href' =&gt; 'link/url',
        '#options' =&gt; array(
          'attributes' =&gt; array(
            'class' =&gt; array('module-link', 'module-link-configure'),
            'title' =&gt; t('Link hover text'),
          ),
        ),
      );
    }
  }
}


Note that you need to change MODULE_NAME to the name of your module and you have the change the link key, text, url, etc. to meet your requirements.

[EDIT]
I have now tested it and it works.
Here is a working example with the placeholder values changed to make a link to google.

/**
 * Implements hook_form_FORM_ID_alter().
 */
function MODULE_NAME_form_system_modules_alter(&amp;$form, &amp;$form_state, $form_id) {
  // Loop through the array of module packages.
  foreach (element_children($form['modules']) as $package) {
    // Loop through the array of module rows for each package.
    foreach (element_children($form['modules'][$package]) as $module_filename) {
      // Add an extra operation link for each module row.
      $form['modules'][$package][$module_filename]['links']['google'] = array(
        '#type' =&gt; 'link',
        '#title' =&gt; t('Google'),
        '#href' =&gt; 'http://google.com',
        '#options' =&gt; array(
          'attributes' =&gt; array(
            'class' =&gt; array('module-link', 'module-link-google'),
            'title' =&gt; t('Go to google'),
          ),
        ),
      );
    }
  }
}


You can also use relative internal links instead of the external google link above.