Legal analysis: the income from pre-marital stock trading is the same property, but the principal of pre-marital stock trading is not the same property.

Legal basis: "Several Specific Opinions of the People's Court on Handling Property Division in the Trial of Divorce Cases" Article 7 If it is difficult to identify personal property or joint property of husband and wife, the party claiming rights shall bear the burden of proof. If the parties fail to produce strong evidence and the people's court cannot verify it, it shall be treated as the joint property of the husband and wife.