Digitalization has brought significant impact in many parts of human life, especially in business activities. Business activities are currently not only held in conventional markets, but have also taken place in E-Commerce. Since there are some differences from the market structure, the parties involved and the use of algorithms complicate the conditions of business competition in E-Commerce so that the compatibility of Act No. 5 of 1999 concerning Prohibition of Monopolistic Practices and Unfair Business Competition should be reviewed. The purpose of this study is to analyse the availability and implementation of laws related to business competition in E-Commerce Platform in Indonesia. The method used in this research is normative juridical supported by empirical juridical. This study found that there are some indications of unfair business competition that occurs in E-Commerce Platform in various forms, one of them is predatory pricing, moreover there is a potential for unfair business competition through the misuse of market power in utilizing consumer data using algorithm. In facing the condition of business competition complexity, this study found that the legal products that currently available are Act No. 5 of 1999 along with Commission Regulations, Chairman's Regulations and Guidelines. In its implementation, KPPU still uses the existing regulations, so that the laws a quo have not been implemented optimally, that means there is still a necessity for laws that regulate strictly and thoroughly related to business competition in E-Commerce Platform.