The shingled magnetic recording (SMR) with exchange coupled composite (ECC) media is a feasible method to achieve the areal density of multi-Tera-bit/in2. However, a rounded corner is inevitable due to deviations from the fabrication process of a shingled writer. The rounded corner is modeled and characterized by two parameters: the rounded angle (θ) and the corner length (L). This paper investigates the influence of the rounded corner effect on the field distribution, writing capability, bit error rate (BER), and erase band width (EBW) of SMR. The analysis suggests that an optimized structure of rounded corner can increase the write field gradient and reduce the stray field to avoid adjacent track encroachment. The results show that if the shingled rounded corner writer with θ = 40° and L = 3 nm is elaborately constructed, the write field gradient can attain a peak value of 552 Oe/nm, and the write performance of the recording system can be improved.