Abstract: In order to study the dynamic characteristics of scroll compressor crankshaft it makes the research of the crankshaft rotor of natural gas scroll compressor and analyzes the displacement and angle of inclination based on modal analysis theory and equation of rotor motion; it also calculates the dynamic coefficients of main shaft bearing and simplifies its using spring-damper system-on the basis of rotor dynamic theory; the prestressed structure modal analysis on scroll compressor crankshaft rotor is made and its vibration performance and mode under the action of the centrifugal force-using finite element analysis through the software ANSYS and at the same time it undertakes modal analyses on crankshaft under different support types and changes the support stiffness of bearing to study its effects on the entire dynamic characteristics of a rotor system. The results indicate that when rigid constraints are applied in the main shaft bearing, rotor of the crankshaft is rigid and its fundamental frequency is far less than first order natural frequency and therefore there is no resonance during working process. Maximum deformation will easily occur at the crank pin and cause substantial effects on scroll compressor’s bearing. We can change the main counterweight’s distance from location of the main bearing to lower crank pin’s deflection. When elastic support is applied in the main shaft bearing, natural frequency of crankshaft rotor is lower compared with rigid constraints and the critical speed of rotation also will be decreased.