The 36-year-old, who has kept new signing Bernd Leno out of the team in the opening four matches, has been criticised for struggling to adapt to Emery's demands for the Gunners to play the ball out of the back consistently.
Cech has been unconvincing at times with the ball at his feet this season and again looked unsettled when he was put under pressure by Cardiff's attackers in his side's 3-2 win in Wales.
Emery, though, insists the former Chelsea man is doing what is required.
"He has experience. He is intelligent. He is doing what we want, to build up our job on the pitch," he told a news conference.
"It's very important for me to continue doing this and to keep improving.
"If you play long balls every time, you lose personality, you lose moments on the pitch. So, for that, we take a little risk, but when you break this risk and break their [the opposition's] pressing on the pitch, you can find space to attack.
"For that, it's clear maybe you can do one mistake, like today, but we need to continue with this personality."
Arsenal were twice pegged back by Cardiff before Alexandre Lacazette fired home the winner nine minutes from time.
Emery thinks the striker is starting to benefit from increasing self-confidence, with the France international having now been involved in 10 goals in his last nine Gunners starts.
"I knew him from Olympique Lyon and I know he has a big capacity to score when the team gives him good chances," said Emery. "He has a very good data for scoring. He showed us. I think many important things happened on the pitch.
"The reaction is very important. We're doing it in each match and today, the same. We needed to win after they [equalised] two times, and I think the reaction was very good.
"They found the chances to score and we need to continue improving in our defensive moments, in the box, not conceding these chances. After that, I think we controlled the match."
Emery also praised the contribution of Mesut Ozil after he was recalled to the starting line-up, having been dropped for last week's 3-1 win over West Ham.
"I give every player the same condition and every player is very important," he said. "But Ozil, with his quality, I think we need him to give us his moments in the match with his quality.
"I think in the second half he played a good match, he worked every minute he was on the pitch.
"Maybe in the second half when we had more control with the ball and in possession, with his position on the pitch, I think he feels better."