This paper proposes a solution to solve Peak-to-Average Power Ratio (PAPR) problem in Orthogonal Frequency Division Multiplexing (OFDM) technique. PAPR problem is caused by each subcarrier modulated by the subcarrier and produces higher ratio between peak power and average power. PAPR resulting higher complexity in analog to digital converter and digital to analog converter and reduce radio frequency (RF) amplifier efficiency. This paper proposes a solution to reduce PAPR by using precoded discrete cosine transform (DCT) that placed before OFDM block system combined with low complexity selected mapping (SLM). The proposed algorithm gives improvement in PAPR reduction in many phase variation.