Tendon and ligament are the transition tissues from a hard tissue to a soft tissue. The regenerative medicine of tendons needs reasonable biomaterials to regenerate precisely from the view point of composition and adhesion properties. In regenerative medicine of hard tissues (e.g. bone, tooth, tendon, ligament), it has been reported that calcifications are influenced by phosphorylated proteins (phosphate groups) and the biomaterial possessing phosphate groups promote or inhibit the formation of HAP. We have studied to develop and evaluate the phosphorylated soft biomaterials, which is possible to control a calcification by the introduction ratio of phosphate groups, as biomaterials for tendon regeneration. In addition, we have studied measurement technologies. In the present study, we studied a FT-IR analysis of gelatins with different introduction ratio of phosphate groups, an evaluation of calcifications by the difference of introduction ratio of phosphate groups, and a fundamental survey on OCT imaging for calcifications of a gelatin and a phosphorylated gelatin. We use phosphorylated gelatins with different introduction ratios of phosphate group linked by ester bonds. The introduction ratios are measured by the Fourier transform infrared spectroscopy (FT-IR) calibrated by a molybdenum blue method. Phosphorylated gelatin sheets were calcified using Simulate Body Fluid (SBF) soaking process and alternative soaking process. These gelatin sheets with different calcification conditions were measured using Spectral Domain Optical Coherence Tomography (SD-OCT) systems with 843nm centered wavelength Super Luminescent Diode (SLD). As a result, we demonstrated that it was possible to measure the calcification on/in the gelatin sheets and sponges and phosphorylated using OCT. The main mechanism is the strong back scattering and the high scattering of deposited calcium particles.