The tree branch Mach-Zehnder interference (MZI) structure 1×32thermo-optic switch array with compact size is proposed and fabricated successfully in this paper.In this work ,the polymer switches were fabricated using the traditional micro-fabrication techniques,including spinning coating, ultra-violet (UV) curing, contact lithography,reactive iron etching (RIE),vacuum evaporating,standard c utting and polish process. By choosing etching parameters and introducing a thin isolating layer between wa veguides and a mask of aluminum,the roughness of the waveguide surface and sidewall is greatly red uced.The fabricated 1×2thermo-optic switch shows insertion loss of 2.84dB, crosstalk of －31.13dB at an applied heating power of 4.1mW.The fabricated 1×32switch array shows insertion loss of 11.8dB,crosstalk of －25.3dB with heating power no more than 5mW.The response time of the switch is 1.15ms .The measured results are in accordance with the numerical simulation.These switche s could be used in optical cross connect (OXC) system,optical add/drop multiplexer (OADM),an d in optica lly controlled phased arrayed antenna systems for beam steering.