Add Multiple images in magento products
Here are the step to Add Multiple images in magento products.

First Go to \app\code\core\Mage\Catalog\Model\Convert\Adapter\Product.php Open Product.php file and find this Code ...

$addedFilesCorrespondence = $mediaGalleryBackendModel -> addImagesWithDifferentMediaAttributes(
$product,
$arrayToMassAdd, Mage::getBaseDir('media') . DS . 'import',
false,
false
);

After this put this code in File

if (isset($importData['media_gallery']) && !empty($importData['media_gallery'])) {
$x = explode(';', $importData['media_gallery']);
foreach ($x as $file) {
$imagesToAdd[] = array('file' =>; trim($file));
}

$mediaGalleryBackendModel -> addImagesWithDifferentMediaAttributes(
$product,
$imagesToAdd, Mage::getBaseDir('media') . DS . 'import',
false,
false
);
}

And Save file. Than open your Product.csv file and Put "media_gallery" Name in one Column and before images like e.g : /s/e/second_image.png, /t/h/third_image.png,/f/o/fourth_image.png . After this updload your csv File.