If a listed company has suffered losses for two consecutive years, with a loss of 1 year, its net assets falling below the par value, or there are major illegal acts in the company's operation, the exchange will give special treatment to the company's shares, that is, the ST system. For ST company, if there is any problem again, such as continuing to lose money in the next year, so that it reaches the limit of loss for three consecutive years in the company law, it is necessary to carry out PT. PT system is a special arrangement adopted by the stock exchange to suspend the stock circulation of listed companies, with the purpose of enhancing market liquidity and earnestly safeguarding the interests of the majority of small and medium-sized investors. When the exchange adopts the PT trading system, it also stipulates that in any 1 year within three years from1,PT companies can apply to the exchange for resumption of listing, and can resume listing after being approved by the China Securities Regulatory Commission.