Different from traditional tax audit,supervision with self-audit is a combination of auditby the taxpayer himself and audit by the tax authority.This paper mainly studies a taxpayer’s optimalpolicy of tax evasion under supervision with self-audit and its related properties,in order to deducesome effective suggestions and theoretical bases to restrain tax evasion.Assuming that only a certainproportion of evaded tax can be discovered when the audit is executed,the authors first formulate astatic model with self-audit.This model is divided into two stages.At the first stage,taxpayers declaretheir taxes,then the tax authority chooses audit objects,based on a known probability,and announcesthe result;if the taxpayer is chosen,he will enter the second stage,during which he has a chance to paythe evaded tax and the corresponding late fees and then is audited by the tax authority.The authorsshow the existence and uniqueness of the optimal amount of tax evasion at the first stage and theoptimal proportion to self-expose at the second stage.The authors also discuss the related propertiesof the interior solution,and do elasticity analyses on some parameters.Besides,the authors extend thestatic model into the corresponding two-period model,and study the existence and uniqueness of thesolution of the extended model.Finally,under the assumption that tax evasion can only be discoveredwith a certain probability when the audit is executed,the authors formulate another static model withself-audit and investigate its properties. Different from traditional tax audit, supervision with self-audit is a combination of auditby the taxpayer himself and audit by the tax authority.This paper mainly studies a taxpayer’s optimalpolicy of tax evasion under supervision with self-audit and its related properties, in order to deducesome effective suggestions and theoretical bases to restrain tax evasion.Assuming that only a certainproportion of evaded tax can be discovered when the audit is executed, the authors first formulate astatic model with self-audit.This model is divided into two stages. At the first stage, taxpayers declaretheir taxes, then the tax authority chooses audit objects, based on a known probability, and announce result; if the taxpayer is chosen, he will enter the second stage, during which he has a chance to paythe evaded tax and the corresponding late fees and then is audited by the tax authority. authors of this existence and uniqueness of the optimal amount of tax evasion at the first stage and theoptimal proportion to self-expose at the second stage.The authors also discuss the related propertiesof the interior solution, and dostiment analyzes on some parameters.Besides, the authors extend thestatic model into the correspondingtwo-period model, and study the existence and uniqueness of thesolution of the extended model .Finally, under the assumption that tax evasion can only be discoveredwith a certain probability when the audit is executed, the authors formulate another static model withself-audit and investigate its properties.