Solidity中uint轉bytes方法如下：

pragma solidity ^0.4.2;

contract Test {
function toBytesNickJohnson(uint256 x) constant returns (bytes b) {
b = new bytes(32);
assembly { mstore(add(b, 32), x) }
}

function toBytesEth(uint256 x) constant returns (bytes b) {
b = new bytes(32);
for (uint i = 0; i < 32; i++) {
b[i] = byte(uint8(x / (2**(8*(31 - i)))));
}
}

function toBytesNicolasMassart(uint256 x) constant returns (bytes c) {
bytes32 b = bytes32(x);
c = new bytes(32);
for (uint i=0; i < 32; i++) {
c[i] = b[i];
}
}

function toBytes(uint256 x) returns (bytes b) {
b = new bytes(32);
assembly { mstore(add(b, 32), x) }
}
}

文章來源：https://ethereum.stackexchange.com/questions/4170/how-to-convert-a-uint-to-bytes-in-solidity