On dashboard page, if you have too many parameters, it will appear url too large, how to deal it?

Nginx is probably the culprit. You can modify the nginx.conf settings to allow longer URLs:

Note: if you run Redash behind any other proxies they will also need to be configured for such long URLs.

Thanks a lot. Maybe we should change this parameters render type. Like hash to compression url.

Possibly. Hash compression implies a tradeoff: worse usability in exchange for a significant increase in the number of parameters on a dashboard. Considering that the workaround is pretty straightforward, it seems easier to fix on an as-needed basis while maintaining URL human readability. The current behaviour is sufficient for 99.99% of users.