Magento 1.8 – Reset Admin Grid Filter Programmatically

Edit grid.php file in your custom module,

By default,

public function __construct()
{
 parent::__construct();
 $this->setId('productsGrid');
 // This is the primary key of the database
 $this->setDefaultSort('id');
 $this->setDefaultDir('ASC');
 $this->setSaveParametersInSession(true);
 $this->setUseAjax(true);
}

Change the code to,

public function __construct()
{
    parent::__construct();
    $this->setId('productsGrid');
    // This is the primary key of the database
    $this->setDefaultSort('id');
    $this->setDefaultDir('ASC');
    $this->setUseAjax(true);
}

If you define grid collection thought layout than you can use updater to add default filter.

<argument name="dataSource" xsi:type="object">
    Tutorial\SimpleNews\Model\Resource\News\Collection
    <updater>Tutorial\SimpleNews\Model\Resource\News\Collection\Updater</updater>
</argument>

and

<?php
namespace Tutorial\SimpleNews\Model\Resource\News\Collection;

class CollectionUpdater implements \Magento\Framework\View\Layout\Argument\UpdaterInterface
{

    /**
     * Update grid collection according to chosen order
     *
     * @param \Tutorial\SimpleNews\Model\Resource\News\Collection $argument
     * @return \Tutorial\SimpleNews\Model\Resource\News\Collection
     */
    public function update($argument)
    {
        $argument->addFieldToFilter('you_field', 'value');

        return $argument;
    }
}

or Extend Grid block

class Grid extends \Magento\Backend\Block\Widget\Grid
{
    protected function _prepareCollection()
    {
        if ($this->getCollection()) {
            foreach ($this->getDefaultFilter() as $field => $value) {
                $this->getCollection()->addFieldToFilter($field, $value);
            }
        }
        return parent::_prepareCollection();
    }   
}