Visual cryptography encodes a secret image into n shares which are distributed to n participants. Pixel sieve method was proposed recently to encode an image into shares, but the encryption quality is poor. In this paper, a modified version of pixel sieve method is proposed to achieve more security than existing pixel sieve method. Based on key shifting scheme, the proposed method generates quite noisy and highly secure encrypted images. The simulation shows that the quality of the encrypted images observably better than existing pixel sieve method.