The invention provides an improved abnormal high-pressure mud rock speed fitting method. The method comprises the steps that mud rock stratum abnormal pressure forming mechanism judgment is conducted;the mud rock density-speed function relation under different abnormal pressure forming mechanism conditions is constructed; and abnormal high-pressure mud rock speed segmented fitting is conducted. According to the provided method, the situation that mud rock stratum density and speed parameters have different related characters under the different abnormal high pressure forming mechanism conditions is considered, the problem that a classic Gardner formula is low in fitting mud rock speed precision is solved, the speed fitting precision of the abnormal high-pressure mud rock can be improved,and accordingly the pressure prediction precision based on speed data is improved.