Guaranty Insurance is a kind of damage insurances and is aiming at compensating to obligee the damage from the default of obligation by obligor. It has the characteristics not only of insurance but also of suretyship that has been ruled repeatedly by supreme court and supported by main stream of theory. The Commercial Act was amended on March this year and is scheduled to be effective on March 12th 2015. Guaranty insurance was one of many insurances that has its source in Insurance Business Act but became to be one of major kinds of insurance of Commercial Act from now on. That amendment included the liability of insurer of guaranty insurance which is related to its definition and clarified some exceptions to guaranty insurance in application of some insurance rules in commercial act, which are §639 ②, §651, §652, §653, §659. And it manifested that some rules in Civil Act can be applied mutatis mutandis to guaranty insurance, which were confirmed by supreme court many times. Referring to the henceforth tasks of guaranty insurance, one of them is clarifying the criterion of differentiating guaranty insurance and quasi-guaranty insurance which are a fraternal insurance, suretyship contract, export guaranty insurance etc. Quasi-guaranty insurance were ruled recently by supreme court so that the differences between real and quasi ones got to have bigger meaning. Next, the monopoly of Seoul Guarantee Insurance in underwriting guaranty insurance contracts was criticized by scholar and business sector. But this paper suggests to take into consideration the essence of guaranty insurance and its influence of its opening on the market and national economy in deciding that policy. And the reduction policy of joint and several liability of guaranty while underwriting guaranty insurance contracts should be enforced after setting up the credit assessment system to prevent from the loss of innocent insurance policy holder. Finally, this paper points out some problems on introducing the privacy policy in guaranty insurance sector,