I estimate that a margin as trading frictions has an effect on the strategies of writing options. The important results are as follows.First, by the margin requirement is increased, the size of short position is reduced. Second, the discrimination of a margin requirement is due to the way that the member margin is imposed less about 1/3 than the customer margin by derivatives market business regulation in KRX. Third, the customer margin is from 1.4 to 1.6 times more than the member margin, and the margin “haircut” ratio is similar to that of the margin. Fourth, by target weight increases, the difference between target weight and effective weight is increased. Fifth, by target weight is increased, the member have higher returns on writing combination position than the customer have. It means that when investors increase the size of short position using all of account, they not only can suffer loss because of margin call but also can make profit.Overall, the difference between the returns of the member and the returns of the customer can be quite substantial. So, this paper contributes to the literature that studies the impact of the different imposition of margins by showing how frictions limit the customer from supplying liquidity to the market and hence releasing pressure on the member.