In the four mask technology based on IGZO TFT-LCD， the influence of drawing design of thin film transistor on actual pattern was studied， and the influence trends of different channel length design and compensation design was obtained on the trailing，shrinkage and film thickness of photoresist in channel area after halftone mask lithography. Results showed that when the value of L was increased from 3 μm to 10 μm， the shrinkage of photoresist was bigger， trailing of photoresist was smaller，and the thickness of photoresist was thinner. However， when L>10 μm， the photoresist shrinkage，trailing and film thickness tended to be stable.Based on the trends above， the effect of the shrinkage and trailing of photoresist could be effectively improved by optimizing the design of channel length and drawing compensation design，and at the same time，the appropriate channel photoresist thickness could be obtained.