The Promise of Chang’an (2020)

Similar love triangle situation, historical setting, political turmoil, dramatic melancholic love stories.

The politic plots, cruel fate of love, the story similar for both of them. The main actor tried hard to protect his lover. I hope this drama will get better ending and fair for all main actor and actress.

Both dramas have the same first and second male leads - Cheng Yi and Han Dong
In both dramas there are Power Struggle nad Fight for the Throne

Both are similar, but not really. If you liked Renascence then you would also like the promise of chang'an.

There's a suspicion among the imperial family to run for the throne. Even though the male lead of both series already take an oath to stay loyal, the suspicion is still exist. Male lead of both dramas are great general who has been spending their life for peace even though suspicion of them beings rebels exists. Both of the drama leads also can't be together in the end because of their priorities and responsibilities.

In the Legend of the Phoenix, the ML and the FL are so in love with each other. When the ML goes to war, the FL promises that she would wait for him to return. But the ML is in grave danger in losing his life unless the FL marries the Emperor. So she marries the Emperor to save the ML. When ML returns from war, he finds his love married. He's in immense sorrow.

Both dramas are based on the same history surrounding Hong Taiji and Da Yu'er. The characters in The Promise of Chang'an are counterparts of historical figures in Qing Dynasty during the respectful time period:
He Lan Mingyu - Da Yu'er
Xiao Chengxu - Dorgon
Xiao Chengru - Hong Taiji
He Lan Wanyin - Ha Lan Zhu
The only significant difference is the Promise of Chang'an is set in a fictitious dynasty rather than the Qing Dynasty due to censorship.
It's also ironic that Han Dong (who played Dorgon in 'In love with Power') plays Xiao Chengrui, Hong Taiji's counterpart.

Both dramas are driven by the female lead who is forced into an arranged marriage between two royal families. She marries someone who is not the love of her life for the sake of her kingdom. The love of her life patiently waits for a chance to redeem that love.

Peace in peace chang’an is similar to the promise of Chang’an because Han dong is in both of these dramas and really amazing

They both have Same male lead actor and same director. And, a lot of actors here are also from Love and Redemption.

Similar storylines and plot. They both have power struggle, political intrigue, and swon brothers. Cinematography and setting are also quite similar.

The storylines are very similar, how a woman's journey to become the most important female figure (Queen) of a country. The South Korean Drama has one female lead and two male lead, just like this one.

Both drama, set in historical period, have a beautiful and interesting plot based on the power struggle.
The female protagonists are both strong, smart and skillful. 
Both drama have a lot of episodes but they are very exiting and not boring.
Princess Wei Young are better in costumes clothing.

Although both dramas could be considered vastly different and have different vibes, there are similar elements. ; Female leads who gain strength through diversities to reach their destinations.

They are both period dramas with lovely setting and heartbreaks that will make you cry and afterwards you will be wandering around to find a drama to replace this one!