how much time to take to see Yiheyuan in Beijing

Yes, you can finish visiting Yiheyuan on the same day.

To reach Yiheyuan, the best transportation method is to use the local subway trains. You can walk to the Dongsi Station easily, where you can take the subway line 6 to reach Xizhimen Station and change to line 4 to reach Beigongmen Station. Get out of the station, you can find Yiheyuan easily.

The subway train journey takes around one hour and twenty minutes. For seeing the palace in general, it takes around two to three hours in the palace. In the palace, the wheel chair service is provided, so you can rent a chair for your husband when traveling inside.

you guided us for going to Yiheyuan from regal Hotel is to take line 6 mrt train from dongsi stn and get down at Xizhimen stn then chage to line 4 but i have seen in subway map that line 6 does not go to Xizhimen stn direct. pl. correct guide us.

Sorry for making such as big mistake.
You can take the line 6 to Ping'anli Station and then change to subway line 4 to Beigongmen Station.