To check the health certificate online, you can follow the steps below:

1. Open the browser: Open your favorite browser, such as Chrome, Firefox, etc.

2. Enter the health certificate query website: Enter the health certificate query website in the browser, such as "China Health Supervision Network" or "National Health and Health Service Platform".

3. Enter the website: After finding the corresponding health certificate query website, click to enter the website.

4. Enter relevant information: In the query page of the website, enter your name, ID number, contact information and other information, and click the "Query" button.

5. Check the results: The system will display your health certificate information, including certificate number, validity period, physical examination hospital, etc.