Significant security vulnerabilities exist at multiple stages of the dynamic linking process. However, existing control flow protection mechanisms provide limited protection for dynamic linking process and suffer from incomplete defense capabilities, high performance overhead, and strong hardware dependence. To address these issues, this study proposes a randomization-based protection mechanism for the dynamic linking process, named SecLoader. Security protection over the full lifecycle of dynamic linking is achieved through three collaborative modules. During the loading stage, a hybrid encryption authentication mechanism is introduced to prevent information leakage and dynamic library hijacking attacks. During symbol resolution, a randomization technique for dynamic library function names is designed to defend against symbol hijacking attacks. During address relocation, a global offset table (GOT) randomization technique is proposed to increase the attack cost of GOT hijacking. The study implements SecLoader in glibc, exhibiting good compatibility and transparency to upper-layer applications. To evaluate defense effectiveness, a penetration attack test set is constructed and real CVE vulnerabilities are used for validation. Furthermore, the study uses the C-language benchmark suite of SPEC CPU 2017 for performance evaluation. Experimental results show that SecLoader effectively mitigates multiple security threats targeting dynamic linking. In terms of performance, only a 42.2% millisecond-level overhead is introduced during program loading, while almost no impact is observed during actual program execution.