The Student of the Year director worked with Khan for his directorial debut Kuch Kuch Hota Hai.
According to IANS, Johar told Oye! 104.8 FM: "When he came on my show Lift Kara De, I was sitting in my black suit. He was very animated, it was a very serious show. Salman said, 'I am not going to sit here, I want to sit on the floor and you will also have to sit on the floor'.
"I am very scared of Salman for some reason, I don't know why, though he has been very wonderful to me, he is close to my family from a very long time, but I get nervous in front of him."
Johar, who launched newcomers Siddharth Malhotra, Varun Dhawan and Alia Bhatt in Student of the Year, said that the young actors often try to emulate Khan.
"These kids want to be like Shah Rukh, I just told them the way SRK shoots, takes the light, does not fumble even once and controls the camera with his eyes... no one, I repeat no one, can ever do that! There is only one Shah Rukh Khan," he said.
Johar admitted he took a risk casting newcomers in his film, but said he needed a new challenge as a director.
Watch the trailer for Student of the Year below: