Rich in numerous nutrients, undaria pinnatifida (UP) exhibited a broad spectrum of biological properties, including anti-inflammatory, anti-bacterial, anti-cancer, and antioxidant properties. A sexual pigment protein complex known as phycocyanin (PC) was the perfect photosensitiser and had no negative effects. Due to their superior qualities, hydrogels were also widely employed in tissue engineering, medication administration, and food packaging at the same time. The aim of this work was to investigate the impact of UVB irradiation on the gel characteristics of PC-UP hydrogels using UVB irradiation technology rather than chemical crosslinking approach. The results showed that the G' value of PC-UP hydrogel increased from 114.17 ± 0.58 Pa to 156.72 ± 0.82 Pa and the G" value increased from 36.80 ± 0.79 Pa to 58.05 ± 1.06 Pa after UVB irradiation. At the same time, the texture properties of hydrogel were significantly improved, and the hardness, adhesion and chewiness were increased to 214.02 ± 3.85, 198.51 ± 4.25 and 195.81 ± 5.69, respectively. After UVB irradiation, hydrogen bond was formed in PC-UP hydrogel to improve its thermal stability. In conclusion, the results show that PC decomposes with alginic acid, potassium salt, and sodium salt in UP under UVB irradiation to form a gel network structure, which enhances its gel properties. This study provides guidance for the photo response of PC-UP hydrogels, provides ideas for the application of PC-UP hydrogels, and broadens the application field of future hydrogels.