every two years前不加介词吗

every two years前面不需要加介词。时间短语中用every加一个时间，不需要介词。例如every morning，every day。 Every two years表示每两年。例如，she comes back to her hometown every two years.她每两年回一次她的家乡。

he goes to Beijing every two years.

every two years前不加介词吗

不加。

比如下面这个句子

The government holds a conference about the solution of the pollution every two years inviting the representatives of the local residents， the media， some experts in this field， and other related parties involved. 政府两年举办一次有关污染解决的大会，被邀请与会的有当地居民代表，媒体，这一领域的一些专家，以及涉及到的其他相关方。