This　paper　focused　on　the　nonholonomic　trajectory　planning　of　underactuated　2R　planar　robot　with　one　actuator.　First　the　dynamics　model　was　built,　the　time-scaling　method　was　used　to　realize　the　point-to-point　trajectory　planning　for　both　active　and　passive　joints.　Then　the　sliding　mode　control　(SMC)　method　which　converged　the　underactuated　system　to　the　planned　manifold　was　introduced　to　achieve　the　feedback　control.　The　SMC　can　overcome　the　shortcoming　of　nonholonomic　systems　that　the　smooth　state　feedback　to　an　equilibrium　point　is　impossible.　Numerical　simulation　results　illuminate　the　effectiveness　of　the　proposed　method.　The　proposed　method　provides　an　effective　way　for　the　trajectory　planning　and　control　of　underactuated　systems.