This research aims to study the parameters that contribute to the crawling performance of the snake robot inside an inclined pipe. The shape and motion propagation of the snake robot directly affect the forward crawling speed of the robot inside a pipe. Motion shape code is proposed as the simplified method for describing shape of a modular snake robot. The motion propagation can be created by shifting the code to the adjacent joint. Five different motion shapes were tested on the 12-joints modular snake robot that moved inside a pipe with varied inclined angles. The experimental results showed that the motion shape that has the maximum number of waves along the robot length and the largest basis angle resulted in the fastest forward crawling speed.