Paper analysises active regulation of microwave to heavy oil by experiment and theory. Determine heavy oil’ rheological indicators before and after . test the composition and structure of heavy oil by the chemical analysis tools, before and after the role of the microwave, analysis the cause of rheological change. Based on the theories of electromagnetic field and the thermodynamic, Establish the mathematical model of microwave effect on heavy oil, determine the experimental temperature distribution inside the heating chamber, and further analysis the mechanism of microwave on heavy oil. Also introduced field application of single-well oil pipeline microwave heater which was development by experiments and theory research. Experimental and theoretical analysis shows that the microwave effect on heavy oil, both have thermal effects and non-thermal effects. Field application shows that microwave is feasible used in heating pipeline in theory, field trials are successful.