To verify a trade company in Zhangjiakou, China, follow these steps:

1. **Legal documents**: Firstly, obtain the business registration certificate or any other official document issued by the local authorities. These documents will typically contain details such as the company name, registered address, and business license number.

2. **Online checks**: Visit official government websites, like the Zhangjiakou City Administration, to conduct online searches. They often have a trade company search function that can verify the authenticity of the company.

3. **Contact verification**: Reach out to the company directly by phone or email. A legitimate business will typically respond promptly and provide accurate information about their company.

By following these steps, you can effectively verify a trade company in Zhangjiakou.